Exhibit 10.501

CHIRON 1991 STOCK OPTION PLAN  AS AMENDED AUGUST 14, 1993, APRIL 11, 1994, FEBRUARY 24, 1995,  MARCH 8, 1996, FEBRUARY 28, 1997, AUGUST 7, 1998, AUGUST 20, 1999,  FEBRUARY 25, 2000, SEPTEMBER 21, 2000, FEBRUARY
16, 2001 AND, JUNE 30 2003

I.     PURPOSES

This Chiron 1991 Stock Option Plan ("Plan") is intended to enable Chiron Corporation ("Corporation") to attract and retain the following individuals by offering
them incentives and rewards, in the form of options, restricted shares, share rights, share units and performance units ("awards") which will encourage them to acquire a proprietary interest in the
Corporation, to continue in the service of the Corporation or its subsidiaries, and to provide incentive to build value for stockholders: (a) employees (including officers and directors) of the
Corporation and its subsidiaries, (b) non-employee members of the Board of Directors of the Corporation ("Board"), and (c) consultants and independent contractors who perform
valuable services for the Corporation and its subsidiaries.

In
addition, the Plan is intended to permit the Corporation to satisfy its obligations in connection with options it assumed pursuant to the terms of the Agreement and Plan of Merger
dated as of July 21, 1991 by and among the Corporation, Chiron Acquisition Subsidiary, Inc., and Cetus Corporation ("Agreement"). Upon consummation of the transactions described in the
Agreement ("Merger"), the Plan superseded Cetus Corporation's Amended and Restated Common Stock Option Plan and Cetus Corporation's Non-Employee Directors' Stock Option Plan ("Cetus Prior
Plans"). Upon stockholder approval in December 1991, this Plan superseded the following Chiron prior plans: the Protos Corporation 1988 Stock Option Plan (upon the merger of Protos into
Chiron), the Chiron Ophthalmics, Inc. 1986 Stock Option Plan (upon the merger of Chiron Ophthalmics into a wholly owned subsidiary of Chiron), the Corporation's 1982 Stock Option Plan and the
Corporation's 1984 Non-Qualified Stock Option Plan (collectively, "Chiron Prior Plans").

II.    ADMINISTRATION

The Plan will be administered by a committee or committees appointed by the Board and consisting of one or more members of the Board or a subcommittee or
subcommittees thereof. The Board may delegate the responsibility for administration of the Plan with respect to designated classes of award holders to different committees, subject to such limitations
as the Board deems appropriate, and each committee may similarly delegate its responsibilities to one or more subcommittees. Members of a committee or subcommittee will serve for such term as the
Board or committee may determine, and will be subject to removal by the Board at any time. With respect to any matter, the term "Committee," when used in this Plan, will refer to the committee or
subcommittee that has been delegated authority with respect to such matter.

In
determining the composition of any committee or subcommittee, the Board or committee, as the case may be, shall consider the desirability of compliance with the compositional
requirements of (i) Rule 16b-3 of the Securities and Exchange Commission with respect to award holders who are subject to the trading restrictions of Section 16(b) of
the Securities Exchange Act of 1934 ("1934 Act") with respect to securities of the Corporation and (ii) Section 162(m) of the Internal Revenue Code ("Code") with respect to performance
units, but shall not be bound by such compliance.

(a)   AUTHORITY.    Each
Committee will have full authority to administer the Plan within the scope of its delegated responsibilities, including authority to
interpret and construe any relevant provision of the Plan, to adopt such rules and regulations as it may deem necessary, and to determine the terms and conditions of awards made under the Plan (which
need not be identical). Decisions of a

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Committee
made within the discretion delegated to it by the Board will be final and binding on all persons who have an interest in the Plan.

III.  ELIGIBILITY FOR AWARDS

(a)   DISCRETIONARY
AWARDS.    From time to time the Committee may, in its discretion, select individuals from among the following categories to receive awards under
the Plan:



(b)   PERFORMANCE
UNITS.    Corporate vice-presidents and other executive officers of the Corporation or a parent or subsidiary ("162(m) executives")
will be eligible to receive performance units in addition to, or in lieu of, other discretionary awards granted under the Plan.

(c)   AUTOMATIC
GRANTS.    Members of the Board who are not employees of the Corporation or a subsidiary will receive awards in accordance with the Plan's automatic
grant provisions.

(d)   SUBSTITUTE
OPTIONS.    Upon consummation of the Merger, outstanding options under the Cetus Prior Plans (including related Limited Stock Appreciation Rights)
were converted, in the manner and at the exchange ratio specified in the Agreement, into substitute options under this Plan to acquire Common Stock (as defined below). Upon stockholder approval and,
with regard to the Protos prior plan options and the Chiron Ophthalmics prior plan options, consummation of the relevant mergers, outstanding options under the Chiron Prior Plans were converted into
options under this Plan. These options preserved the exercise price of the outstanding options as adjusted, in the case of options under the Protos Corporation 1988 Stock Option Plan and the Chiron
Ophthalmics, Inc. 1986 Stock Option Plan, to reflect the substitution of Common Stock. These options also preserved the other terms and conditions of the outstanding options; provided, however,
that on the Effective Date of this Plan, outstanding automatic option grants under the Corporation's 1982 Stock Option Plan were conformed, other than to extend the term, to the Automatic Option
Grants under this Plan. Collectively, these options are referred to as "Substitute Options."

IV.    STOCK SUBJECT TO THE PLAN

(a)   CLASS.    The
stock subject to awards under the Plan is (i) the Corporation's authorized but unissued or reacquired Common Stock ("Common Stock"), or
(ii) shares of one or more series of the Corporation's authorized but unissued or reacquired Restricted Common Stock, in the aggregate, "Company Stock." In connection with the grant of awards
under the Plan, the Corporation may repurchase shares in the open market or otherwise.

(b)   AGGREGATE
AMOUNT



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(c)   ADJUSTMENTS.    In
the event any change is made to the Company Stock subject to the Plan (whether by reason of merger, consolidation, reorganization,
recapitalization, stock dividend, stock split, combination of shares, exchange of shares, or other change in corporate or capital structure of the Corporation affecting the outstanding Common Stock as
a class without the Corporation's receipt of consideration) then, unless such change results in the termination of all awards, the Committee will make appropriate adjustments to (i) the number
and/or class of securities available under the Plan, (ii) the number and/or class of securities for which any one person may be granted awards under the Plan, (iii) the number and/or
class of securities to be made under automatic grants to non-employee directors, and (iv) the number and/or class of securities and, where applicable, price per share of securities
subject to outstanding awards. Such adjustments are to be effected in a manner which shall preclude the enlargement or dilution of rights and benefits of awards and shall be final, binding and
conclusive.

V.     TERMS AND CONDITIONS OF DISCRETIONARY OPTIONS

Discretionary stock options granted under the Plan may, in the Committee's discretion, be either incentive stock options ("Incentive Options") qualifying under
Section 422 of the Internal Revenue Code of 1986, as amended ("Internal Revenue Code"), or nonstatutory options. Individuals who are
not employees of the Corporation or its subsidiaries may only be granted nonstatutory options. Options will be evidenced by instruments in such form as the Committee may from time to time approve.
These instruments will conform to the following terms and conditions and, in the discretion of the Committee, may contain such other terms, conditions and restrictions as are not inconsistent with the
following:

(a)   OPTION
PRICE.    The option price per share will be fixed by the Committee, but in no event will the option price per share be less than
eighty-five percent (85%) of the Fair Market Value of the option shares on the date of the option grant; provided, however, that in no event will the option price per share of an Incentive
Option be less than one hundred percent (100%) of the Fair Market Value of the option shares on the date of the option grant. However, the Committee may grant options with an option price per share
less than eighty-five percent (85%) of the Fair Market Value of the option shares on the date of the option grant in substitution for the outstanding options of the acquired company in a
merger, if such options are granted with an option price per share which preserves the option price of the outstanding options, as adjusted for the merger. Notwithstanding the foregoing, Substitute
Options will have an option price per share determined pursuant to Section III(d) of this Plan.

(b)   NUMBER
OF SHARES, TERM AND EXERCISE TERM AND NUMBER.    Each option granted under the Plan will be exercisable on such date or dates, during such period, and
for such number of shares of Company Stock as the Committee determines and sets forth in the instrument evidencing the option. No option granted under the Plan will have an expiration date that is
more than 10 years after the date of the option grant.



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(c)   TERMINATION
OF SERVICES.    The Committee will determine and set forth in each option whether the option will continue to be exercisable, and the terms and
conditions of such exercise, on and after the date that an optionee ceases to be employed by, or to provide services to, the Corporation or its subsidiaries. The date of termination of an optionee's
employment or services will be determined by the Committee, which determination will be final.

(d)   INCENTIVE
OPTIONS.    Options granted under the Plan that are intended to be Incentive Options will be subject to the following additional terms and
conditions:



(e)   WITHHOLDING



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VI.   DISCRETIONARY RESTRICTED SHARES, SHARE RIGHTS, SHARE UNITS AND PERFORMANCE UNITS

(a)   NATURE
OF AWARDS



(b)   WITHHOLDING.    The
Committee may require, or permit an award holder to elect, that a portion of the total value of the shares of Common Stock subject to
restricted shares or share rights held by one or more award holders be paid in the form of cash in lieu of the issuance of Company Stock and that such cash payment be applied to the satisfaction of
the federal, state and local income and employment tax withholding obligations that arise at the time the restricted shares and share rights become free of all restrictions under the Plan.

(c)   CASH
PAYMENTS.    The Committee may provide award holders with an election to receive a percentage of the total value of the Company Stock subject to
restricted shares or share rights in the form of a cash payment, subject to such terms, conditions and restrictions as the Committee shall specify.

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(d)   ELECTIVE
AND TANDEM AWARDS.    The Committee may award restricted shares, share rights, and share units independently of other compensation or in lieu of
compensation that would otherwise be paid in cash or stock options, whether at the election of the potential award holder or otherwise. The number of restricted shares, share rights or share units to
be awarded in lieu of any cash compensation amount or number of stock options shall be determined by the Committee in its sole discretion and need not be equal to such foregone compensation in Fair
Market Value. In addition, restricted shares, share rights, and share units may be awarded in tandem with stock options, so that a portion of such award becomes payable or becomes free of restrictions
only if and to the extent that the tandem options are not exercised or are forfeited, subject to such terms and conditions as the Committee may specify.

(e)   MODIFICATION
OF AWARDS.    Except to the extent an award is granted as a performance unit, the Committee may, in its sole discretion, modify or waive any or
all of the terms, conditions or restrictions applicable to any outstanding restricted share, share right or share unit; provided, however, that no such modification or waiver shall, without the
consent of the holder of an outstanding award, adversely affect the holder's rights thereunder.

(f)    PERFORMANCE
UNITS.    Effective March 8, 1996, the Committee may grant restricted shares, share rights and share units to 162(m) executives that comply
with the requirements of Code Section 162(m). Performance units will become payable or vest upon attainment of specified performance goals over a specified performance period.



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VII. AUTOMATIC AWARDS TO DIRECTORS

(a)   OPTIONS.    Effective
on and after June 30, 2003, non-employee members of the Board ("Eligible Directors") will automatically be granted
nonstatutory options to purchase the number of shares of Common Stock determined as set forth below (subject to adjustment under Section IV(c) hereof) on the dates and terms set forth below:



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(b)   SHARE
RIGHTS.    Effective on and after June 30, 2003, Eligible Directors will automatically be granted a number of share rights determined as set forth
below (subject to adjustment under Section IV(c) hereof) on the dates and terms set forth below:



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VIII. LOANS AND INSTALLMENT PAYMENTS

In order to assist an award holder (including an employee who is an officer or director of the Corporation) in the acquisition of shares of Company Stock pursuant
to an award granted under the Plan (other than pursuant to the Automatic Option Grant provisions of this Plan), the Committee may authorize, at either the time of the grant of an award or the time of
the acquisition of Company Stock pursuant to the award (i) the extension of a loan to the award holder by the Corporation, (ii) the payment by the award holder of the purchase price, if
any, of the Company Stock in installments, or (iii) the guarantee by the Corporation of a loan obtained by the award holder from a third party. The terms of any loans, guarantees or installment
payments, including the interest rate and terms of repayment, will be subject to the discretion of the Committee. Loans, installment payments and guarantees may be granted without security, the
maximum credit available being the purchase price, if
any, of the Company Stock acquired plus the maximum federal and state income and employment tax liability that may be incurred in connection with the acquisition.

IX.   ASSIGNABILITY

No award granted under the Plan is assignable or transferable by the award holder other than by Will or by the laws of descent and distribution, and during the
lifetime of the award holder, only the award holder may exercise options or exercise the rights provided under awards granted under the Plan. However, if and to the extent that the Committee so
authorizes at the time an award is granted or amended, an option (other than an option designated as an Incentive Option) or other award may be assigned in whole or in part during the grantee's
lifetime to one or more of the grantee's family members or an entity substantially owned, benefiting or controlled by the grantee or one or more of grantee's family members if and to the extent that
the Securities and Exchange Commission Form S-8 Registration Statement would continue to be available for the exercise of the award and resale of the underlying securities following
such assignment. The terms applicable to the assigned portion shall be the same as those in effect for the award immediately prior to such assignment and shall be set forth in such documents issued to
the assignee as the Committee may deem appropriate.

X.    CANCELLATION AND NEW GRANT OF OPTIONS

The Committee will have the authority to effect, at any time and from time to time, with the consent of the affected option holders, the cancellation of any or
all outstanding options under the Plan, a Cetus Prior Plan or a Chiron Prior Plan (other than options granted under automatic option

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grant
provisions of these plans) and to grant in substitution therefor new options under the Plan covering the same or different numbers of shares, but having an option price per share not less than
eighty-five percent (85%) of the Fair Market Value on the new grant date or, in the case of an Incentive Option, one hundred percent (100%) of the Fair Market Value on the new grant date
(or, in the case of an Incentive Option granted to a 10% Stockholder, one hundred ten percent (110%) of such Fair Market Value).

XI.   ACCELERATION AND TERMINATION OF AWARDS

(a)   ACCELERATION.    If
the Corporation or its stockholders enter into an agreement to dispose of all or substantially all of the assets of the Corporation, enter
into an agreement to merge or consolidate with another entity or enter into a plan of reorganization or liquidation, each award will be automatically accelerated so that (1) options become
fully exercisable with respect to the total number of shares purchasable under the options; (2) restrictions on restricted shares will be eliminated, and the shares will immediately vest; and
(3) share rights and share units will immediately vest and become payable. The Committee may also provide for the automatic termination of repurchase rights upon the occurrence of such an
event.

(b)   NO
ACCELERATION.    No acceleration of awards will occur if the terms of the agreement require that each such award either be assumed by the successor
corporation or parent thereof or be replaced with a comparable award subject to shares of the successor corporation or parent thereof. The determination of such comparability will be made by the
Committee, and its determination will be final, binding and conclusive. Upon consummation of the transaction contemplated by the agreement, all awards, whether or not accelerated, will terminate
unless assumed pursuant to a written agreement by the successor corporation or parent thereof. However, nothing in this Section will prohibit the Committee from granting an award that provides for the
acceleration of exercisability and/or vesting of the award either (i) upon the occurrence of any specified event, including a corporate transaction or change in control of the Corporation (as
defined by the Committee) whether or not the award is assumed or replaced with a comparable award or (ii) upon termination of employment or other occurrence following such an event.

(c)   CORPORATE
STRUCTURE.    The grant of awards under this Plan will in no way affect the right of the Corporation to adjust, reclassify, reorganize, or otherwise
change its capital or business structure or to merge, consolidate, dissolve, liquidate or sell or transfer all or any part of its business or assets.

XII. VALUATION

With regard to all Substitute Options, Fair Market Value will be determined in accordance with the relevant option plan documents on the date that the outstanding
options were granted. With regard to awards granted under this Plan, for all valuation purposes under the Plan, the Fair Market Value of a share of Common Stock or Restricted Common Stock (as the case
may be) on any relevant date will be determined in accordance with the following provisions:

(a)   If
the Common Stock or Restricted Common Stock is not at the time listed or admitted to trading on any stock exchange, but is traded in the
over-the-counter market, the Fair Market Value will be the average between the reported high price and the reported low price of one share of Common Stock or Restricted Common
Stock (as the case may be) on the date in question in the over-the-counter market, as such prices are reported by the National Association of Securities Dealers through its
NASDAQ system or any successor system.

(b)   If
the Common Stock or Restricted Common Stock is at the time listed or admitted to trading on any stock exchange, then the Fair Market Value will be the average between
the reported high price and the reported low price of one share of Common Stock or Restricted Common Stock (as the case

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may
be) on the date in question on the stock exchange that is the primary market for the stock, as such prices are officially quoted on such exchange.

(c)   If
the Common Stock or Restricted Common Stock (as the case may be) is at the time neither listed nor admitted to trading on any stock exchange nor traded in the
over-the-counter market, or if the Committee determines that neither subparagraph (a) nor subparagraph (b) above reflects Fair Market Value of the stock and the
award was not granted pursuant to the Plan's Automatic Award provisions, then the Fair Market Value will be determined by the Committee after taking into account such factors as the Committee deems
appropriate, or in the case of Automatic Awards, by an independent third party valuation.

XIII. SURRENDER OF OPTIONS FOR CASH OR STOCK

(a)   STOCK
APPRECIATION RIGHTS.    If, and only if the Committee, in its discretion, elects to implement an option surrender program under the Plan, one or more
option holders may, upon such terms and conditions as the Committee may establish at the time of the option grant or at any time thereafter, be granted the right to surrender all or part of an
unexercised option in exchange for a distribution equal in amount to the difference between (i) the Fair Market Value (at date of surrender) of the shares for which the surrendered option or
portion thereof is at the time exercisable and (ii) the aggregate option price payable for such shares. The distribution to which an option holder becomes entitled under this Section may be
made in shares of Common Stock or Restricted Common Stock, valued at Fair Market Value at the date of surrender, in cash, or partly in shares and partly in cash, as the Committee, in its sole
discretion, deems appropriate. The option surrender provisions of this Section will not apply to options granted pursuant to the Automatic Option Grant provisions of this Plan.

(b)   LIMITED
STOCK APPRECIATION RIGHTS.    If outstanding options of Cetus for which Substitute Options are issued pursuant to Section III(d) have Limited
Stock Appreciation Rights ("LSARs") attached thereto, then each such LSAR shall be honored by the Corporation in accordance with its terms and remain exercisable for a period of 60 days
following the date that stockholders of Cetus approve the Merger; provided, however, that if the LSAR was originally granted within 6 months of the date that Cetus stockholders approve the
Merger, then the LSAR will be exercisable for a period of 60 days following expiration of such six-month period. Upon expiration of the applicable 60-day period, each
such LSAR not previously exercised shall expire. Upon exercise of an LSAR, the related option will be cancelled, and Chiron will pay to the LSAR holder an amount in cash for each share with respect to
which the LSAR is exercised determined in accordance with the terms of the Cetus Prior Plans.

XIV. REPURCHASE RIGHTS

The Committee may, in its discretion, establish as a term of one or more awards granted under the Plan that the Corporation (or its assigns) will have the right,
exercisable upon the award holder's termination of employment with, or cessation of services for, the Corporation and its subsidiaries, to repurchase at the original price paid, if any, for such
shares of (1) Company Stock acquired by the award holder pursuant to the granted award, or (2) Common Stock into which acquired Restricted Common Stock may have been converted or for
which Restricted Common Stock may have been exchanged. Any such repurchase right will be exercisable by the Corporation (or its assigns) upon such terms and conditions (including provisions for the
expiration of such right in one or more installments) as the Committee may specify in the instrument evidencing such right. The Committee will also have full power and authority to provide for the
automatic termination of the Corporation's repurchase rights, in whole or in part, thereby accelerating the vesting of any or all of the purchased shares (other than purchased shares obtained pursuant
to the Automatic Award provisions of this Plan) upon the occurrence of any change in control specified in Article XI.

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XV.  RIGHT OF FIRST REFUSAL

The Committee may, in its discretion, establish as a term of one or more awards granted under the Plan that the Corporation has a right of first refusal with
respect to the proposed disposition by the award holder (or any successor in interest by reason of purchase, gift or other mode of transfer) of any shares of (1) Company Stock acquired by the
award holder pursuant to the granted award, or (2) Common Stock into which purchased Restricted Common Stock may have been converted or for which acquired Restricted Common Stock may have been
exchanged. Any such right of first refusal will be exercisable by the Corporation or its assigns in accordance with the terms and conditions specified in the instrument evidencing such right.

XVI. EFFECTIVE DATE AND TERM OF PLAN

(a)   EFFECTIVE
DATE.    The Plan became effective on December 10, 1991, the date that it was approved by the Corporation's stockholders. The Plan was
subsequently amended on several occasions and, as amended through March 8, 1996, was approved by the Corporation's stockholders on May 16, 1996. The Plan was further amended on
February 28, 1997, and as amended through February 28, 1997 was approved by the Corporation's stockholders on May 15, 1997. The Plan was subsequently amended on a number of
occasions and was further amended on February 16, 2001 to (i) eliminate the automatic share rights awards to Eligible Directors contained in then Section VII (b) of the
Plan, (ii) change the annual automatic option grant to non-employee directors from an option to purchase a number of shares of Common Stock determined by dividing $100,000 by the
average stock price of a share of Common Stock over the preceding 12 months to an option to purchase 15,000 shares of Common Stock, and reduce the vesting schedule for such option from
5 years to 6 months, and (iii) implement an initial option grant feature, whereby each newly elected or appointed non-employee director automatically receives an
option grant to purchase 30,000 shares of Common Stock which vests over a 3-year period. The Plan was amended on June 30, 2003 to (i) eliminate the annual 15,000 share
automatic option grant to non-employee directors, (ii) implement an automatic share right grant feature, whereby each continuing non-employee director automatically
receives on the last business day of April each year (or with respect to the 2003 year, June 30, 2003) a number of share rights equal to $160,000 worth of Common Stock (or if such
non-employee director has not completed a full year of board service prior to the applicable grant date, a pro-rated award based on the number of whole calendar months of board
service completed prior to the grant date) and (iii) change the initial automatic option grant to non-employee directors to eliminate the ability to exercise such options prior to
vesting in the shares subject to the option and to impose a transfer restriction on certain shares purchased pursuant to the option until the non-employee director holds $500,000 worth of
vested shares of Common Stock.

(b)   TERM.    Incentive
Options may be granted under the Plan until May 14, 2007, and may not be issued under the Plan after that date. Subject to this
limitation, the Committee may grant awards under the Plan at any time after the Effective Date of the Plan and before the Plan is terminated by the Board.

XVII. AMENDMENT OR DISCONTINUANCE

(a)   BOARD.    The
Board may amend, suspend or discontinue the Plan in whole or in part at any time; provided, however, that (a) except to the extent
necessary to qualify as Incentive Options any or all options granted under the Plan that are intended to so qualify, such action may not, without the consent of the award holder, adversely affect
rights and obligations with respect to awards outstanding under the Plan; (b) certain amendments may, as determined by the Board in its sole discretion, require stockholder approval pursuant to
applicable laws or regulations.

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(b)   COMMITTEE.    The
Committee will have full power and authority to modify or waive any or all of the terms, conditions or restrictions applicable to any
outstanding award (other than Automatic Option Grants), to the extent not inconsistent with the Plan.

(c)   SUBSTITUTE
OPTIONS.    Substitute Options will be subject to amendment in accordance with the terms of this Plan.

XVIII. NO OBLIGATION

Nothing contained in the Plan (or in any award granted under this Plan, a Chiron Prior Plan or a Cetus Prior Plan) shall confer upon any employee, consultant, or
independent contractor any right to continue in the employ of, or to provide services to, the Corporation or any affiliate or constitute a contract or agreement of employment or for the provision of
services, or interfere in any way with the right of the Corporation or an affiliate to reduce such employee's, consultant's or independent contractor's compensation from the rate in existence at the
time of the granting of an award or to terminate such employee's, consultant's or independent contractor's employment or services at any time, with or without cause; but nothing contained in the Plan
or in any award granted under this Plan shall affect any contractual rights of an employee pursuant to a written employment agreement.

XIX. USE OF PROCEEDS

The cash proceeds received by the Corporation pursuant to awards granted under the Plan will be used for general corporate purposes.

XX. COMPLIANCE

(a)   FEDERAL
AND STATE LAWS.    No option may be exercised, and the Corporation will not be obligated to issue stock under any award unless, in the opinion of
counsel for the Corporation, such exercise and issuance is in compliance with all applicable federal and state securities laws. As a condition to the grant of any award, or to the issuance of stock
under any award, the Committee may require that the award holder agree to comply with such provisions of federal and state securities laws as may be applicable to such grant, or to the sale of stock
acquired pursuant to the Plan, and that the award holder deliver to the Corporation a written agreement, in form and substance satisfactory to the Corporation and its counsel, implementing such
agreement.

(b)   INFORMATION.    The
Corporation will furnish to each award holder participating in the Plan (other than a key employee or a director) a copy of the
Corporation's Annual Report to Stockholders for the most recent fiscal year, and additional copies will be furnished, without charge, to such award holders upon request to the Secretary of the
Corporation.

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APPENDIX A  SPECIAL PROVISIONS RELATED TO 1995 CIBA-GEIGY TRANSACTION

Those
persons holding options to acquire shares of Common Stock under the Corporation's 1991 Stock Option Plan on November 20, 1994 are granted the following rights ("Rights")
with respect to each such option:



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