Document:

Exhibit 4b

                      SECOND AMENDMENT TO RIGHTS AGREEMENT

THIS SECOND  AMENDMENT TO RIGHTS  AGREEMENT dated as of January 28, 2000, by and
between Atrion Corporation,  a Delaware corporation (the "Company") and American
Stock Transfer & Trust Company (the "Rights Agent").

                                    RECITALS

A. The Company and the Rights Agent are parties to that certain Rights Agreement
dated as of February 1, 1990, as heretofore amended (the "Rights Agreement").

B. The Rights  Agreement  provides  that the  Rights  (as  defined in the Rights
Agreement)  may be  exercised  after the  Distribution  Date (as  defined in the
Rights  Agreement) at or prior to the earliest to occur of the close of business
on  February  1, 2000 which is defined  as the "Final  Expiration  Date" and two
other events set forth therein.

D. The Board of Directors of the Company desires to extend the Final  Expiration
Date until February 1, 2005.

NOW THEREFORE,  in consideration of the mutual agreements set forth herein,  and
in  accordance  with  Section 27 of the Rights  Agreement,  the  Company and the
Rights Agent hereby agree as follows:

1.  Clause (i) of  Section  7(a) of the Rights  Agreement  is hereby  amended by
deleting  said clause in its entirety  and  substituting  the  following in lieu
thereof:

  "(i) the close of business on February 1, 2005 (the "Final Expiration Date"),"

2. Except as amended hereby, the Rights Agreement shall remain in full force and
effect.

IN WITNESS WHEREOF,  the parties have executed this Second Amendment on the date
first written above.

                                         ATRION CORPORATION

                                             -----------------------------
                                         By: /s/ Emile A. Battat
                                           Its Chairman and President

                                         AMERICAN STOCK TRANSFER & TRUST
                                         COMPANY

                                             -----------------------------
                                         By: /s/ Herbert J. Lemmer
                                           Its Vice PresidentExhibit 10j

                        OPTION AGREEMENT FOR THE PURCHASE
                            AND SALE OF REAL PROPERTY

         THIS  AGREEMENT  is made as of the 30th day of  January,  1998,  by and
between QUEST MEDICAL,  INC., a Texas  corporation  ("Quest"),  and QMI MEDICAL,
INC. (formerly QMI Acquisition Corp.), a Texas corporation ("Buyer").

                                    RECITALS

         Quest is the owner of certain real property  located in Collin  County,
Texas,  more  particularly  described on Exhibit A attached hereto, a portion of
which  has  been   condemned   and   purchased  by  the  Texas   Department   of
Transportation, as set forth on Exhibit A (the "Property") and, pursuant to that
certain Asset Purchase  Agreement  among Buyer,  Atrion  Corporation,  and Quest
dated as of December 29, 1997 (the "Asset Purchase Agreement"), Buyer intends to
acquire  certain assets used in connection with the Property which are set forth
on Exhibit B attached hereto (the "Real Property Assets").

         In  connection  with the  purchase  and  sale of  assets  provided  for
therein,  the  parties  intend  to enter  into a Lease  Agreement  covering  the
Property and the Real Property Assets (the "Lease").

         Quest  desires  to grant to Buyer an option to  purchase  the  Property
subject to terms and conditions set forth below.

         In the event Buyer does not exercise  the  aforementioned  option,  the
Buyer  agrees to sell and Quest  agrees to purchase  the Real  Property  Assets,
subject to the terms and conditions set forth below.

         All capitalized  terms used herein and not otherwise defined shall have
the meanings given to them in the Asset Purchase Agreement.

         NOW  THEREFORE,  in  consideration  of  the  premises  and  the  mutual
covenants set forth below, the parties hereby agree as follows.

         1. OPTION TO PURCHASE.  Subject to the terms and conditions hereinafter
set  forth,  Quest  does  hereby  give and grant to Buyer,  its  successors  and
assigns,  the exclusive  continuing  option and right to buy (the  "Option") the
Property,  together  with  all  interest  of  Quest  in and  to  all  buildings,
improvements, fixtures, easements and appurtenances pertaining thereto.

         2.  TERM.  The term of the  Option  shall  be for a period  of nine (9)
months beginning on the date of Closing under the Asset Purchase  Agreement (the
"Option Period").  The Option shall be exercisable by delivering  written notice
to Quest at the address and in the manner  provided for notices set forth in the
Asset  Purchase  Agreement.  If the  Option is not

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exercised  within the Option Period,  all rights and obligations  hereunder will
terminate as to all parties and their assignees except as otherwise set forth in
paragraph 12 below.

         3. CONSIDERATION. In the event Buyer elects to exercise the Option, the
purchase price (the "Purchase Price") for the Property shall be Six Million Five
Hundred Thousand and 00/100 Dollars  ($6,500,000.00)  subject to the adjustments
provided  herein and  prorations  at closing and subject to a deduction  for any
debt assumed pursuant to paragraph 5 below.

         4.       CLOSING.

         (a) Date of Closing.  The  consummation of the purchase and sale of the
Property  is  referred  to herein as the  "Property  Closing."  If the Option is
exercised as provided herein, the Property Closing shall occur on the earlier of
(i) the date  which is six (6)  months  after  the date of the  exercise  of the
Option or (ii) the expiration of the term of the Lease, such Property Closing to
take place at the offices located at the Property.

         (b) Conveyance.  Quest shall convey, by special warranty deed, good and
indefeasible  fee simple title to the  Property  free and clear of all liens and
encumbrances  except for the Permitted Liens (as defined below). As used herein,
the term "Permitted Liens" shall mean any of the following:  (i) liens for taxes
not yet due and payable,  (ii) easements,  encroachments and encumbrances listed
in the draft title  commitment  dated  November 4, 1997 issued by Lawyers  Title
Insurance  Corporation,  a copy of which is  attached  hereto as  Exhibit C (the
"Title  Commitment"),  (iii)  liens in favor of  MetLife  if assumed by Buyer in
accordance with paragraph 5 below,  and (iv) zoning,  entitlement,  building and
other  land  use  regulations   imposed  by  Governmental   Authorities   having
jurisdiction  over the  Property.  Quest  covenants  that,  except as  otherwise
disclosed in the Title Commitment,  it has not assigned or conveyed and will not
assign or convey any interest,  including,  without limitation,  any easement or
leasehold interest, in the Property or permit any liens or other encumbrances to
attach thereto prior to the Property Closing.

         If there  should  be  filed  against  the  Property  any  such  lien or
encumbrance or if, any exception to title appears in the Title  Commitment other
than a Permitted Lien, Buyer may elect either (i) to rescind this Option or (ii)
to close  the  purchase  and  sale  transaction  without  regard  to such  title
objections but with a mutually-agreed  upon adjustment to the Purchase Price. If
the parties are unable to agree upon such adjustment, then such dispute shall be
resolved by arbitration as provided in paragraph 11 below.  Liens  affecting the
Property (other than the Permitted Liens) which are dischargeable by the payment
of money shall be paid by Quest at the  Property  Closing.  Additionally,  Quest
covenants to maintain the Property in good condition and repair, normal wear and
tear  excepted.  In the event of a breach of the foregoing  covenant,  Buyer may
elect  either (i) to rescind  this Option or (ii) to close the purchase and sale
transaction  without  regard  to such  damage  but with a  mutually-agreed  upon
reduction- in the Purchase Price. If the 2 parties are unable to agree upon such
adjustment,  then such dispute shall be resolved by  arbitration  as provided in
paragraph 11 below.

         (c)  Property  Closing  Documents.  At the  Property  Closing  and as a
condition

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<PAGE>

precedent   thereto,   the  parties  shall  execute  and  deliver  such  closing
statements,  affidavits and other documents necessary to consummate the purchase
and sale of the  Property  pursuant  to the  terms  hereof,  including,  without
limitation,  a certificate  of Quest  certifying  that the  representations  and
warranties  contained  in  Sections  3.9,  3.10 and 3.15 of the  Asset  Purchase
Agreement  are true and correct as of the date of the  Property  Closing.  Quest
shall use its  reasonable  good faith efforts to revise the Title  Commitment in
accordance  with the  memorandum  attached  hereto (the Title  Commitment  as so
revised being hereinafter referred to as the "Revised Title Commitment").  Quest
shall deliver to Buyer at the Property  Closing a title commitment that conforms
to the Title  Commitment  (or the  Revised  Title  Commitment  if Quest has been
successful  in obtaining the  aforementioned  revisions),  with such  additional
changes as may be acceptable  to Quest and Buyer,  subject only to the Permitted
Liens. Quest and Buyer shall share equally the fee for such title policy.

         (d) Property  Closing  Costs and  Prorations.  Buyer shall pay any deed
taxes and recording  fees imposed on the conveyance of the Property and one-half
of the title insurance premium.  Quest shall pay one-half of the title insurance
premium.  Each party shall be responsible for its own legal fees and costs.  All
real estate ad valorem taxes for the year in which the Property  Closing  occurs
shall be prorated as of the date of the Property Closing. All unpaid assessments
applicable to the Property assessed as of the date of the Property Closing shall
be paid at the Property  Closing by Quest without  regard to when the same shall
be due and payable.  Any assessments arising after the Property Closing shall be
the sole  responsibility  of Buyer.  The provisions of this paragraph 4(d) shall
survive the Property Closing.

         (e) Possession. Subject to any term of the Lease to the contrary, Quest
shall  deliver  sole  possession  of the  Property  to  Buyer on the date of the
Property Closing.

         5. METLIFE MORTGAGE. The parties acknowledge that as of the date hereof
the  Property and certain  furniture,  fixtures,  equipment  and the HVAC system
located on the  Property  are subject to liens  securing  the MetLife  Mortgage.
Buyer, at its sole option, may assume the MetLife Mortgage and accept conveyance
of the Property subject thereto, and in such event, such liens shall continue to
encumber  the  Property  and shall be a  Permitted  Lien.  If Buyer  assumes the
MetLife Mortgage, such assumption will be given innovation and extinguishment of
Quests  obligations  thereunder.  If Buyer does not elect to assume the  MetLife
Mortgage,  Quest shall  transfer  the  Property  and such  furniture,  fixtures,
equipment  and HVAC  system  to Buyer  free and  clear of any  liens in favor of
MetLife to Buyer. Quest and Buyer shall share equally any assumption fee charged
by MetLife.

         6. TAX  ABATEMENT  AGREEMENT.  After  receipt  of the  notice of Buyers
exercise of the Option and prior to the  Property  Closing,  Quest shall use all
reasonable  efforts  and do all  things  necessary  or  advisable  to  obtain an
assignment  to and  assumption  by Buyer of the Tax  Abatement  Agreement and an
agreement  from the City of Allen  and The  Allen  Independent  School  District
waiving all Taxes abated for periods prior to January 1, 1998. If Quest does not
obtain such assignment of the Tax Abatement Agreement and the waiver referred to
in the immediately  preceding sentence,  Quest shall indemnify and hold harmless
Buyer to the extent such abated Taxes are assessed to and required to be paid by
Buyer for  periods  prior to January 1, 1998.  In the event Buyer is notified by
any taxing authority that

                                      -47-
<PAGE>

such abated Taxes are required to be paid,  Quest shall either pay the amount of
such abated Taxes directly to the taxing  authority  within the time  designated
for payment or pay such amount to Buyer within five (5) business days  following
Buyer's written notice to Quest.

         7. ASSIGNMENT. Buyer may assign its rights hereunder, provided that any
such assignment shall not release Buyer from its obligations  hereunder and that
written  notice  of such  assignment  shall be given to  Quest.  Subject  to the
preceding  sentence,  this  agreement  shall be  binding  upon and  inure to the
benefit of the successors and assigns of the parties hereto.

         8. NOTICES.  All communications,  notices and demands of any kind which
either  party may desire or be required to give or to serve upon the other party
shall be made in writing and  delivered  to such party at the address and in the
manner set forth in the Asset Purchase Agreement for the giving of notices.

         9. RISK OF LOSS.

         (a) The risk of loss, damage or destruction to the Property, including,
without  limitation,  any loss or damage due to the location or placement of any
substance  regulated  by local,  state or federal  law,  shall remain with Quest
until the date of the Property  Closing.  Quest shall deliver  possession of the
Property at the Property  Closing in the same condition  existing on the date of
complete  execution hereof,  except for normal wear and tear, and Buyer shall be
responsible  for any damage to the Property caused by Buyer. In the event of any
loss,  damage or destruction to the Property  occurring prior to the date of the
Property  Closing (other than damaged  caused by Buyer),  Buyer may elect either
(i) to rescind this Option or (ii) to close the  purchase  and sale  transaction
without regard to such loss,  damage or destruction  but with a mutually  agreed
upon  reduction in the Purchase  Price.  If the parties are unable to agree upon
such adjustment,  then such dispute shall be resolved by arbitration as provided
in paragraph 11 below.

         (b) The risk of loss, damage or destruction to the Real Property Assets
shall  remain with Buyer until the Real  Property  Assets are  conveyed to Quest
pursuant to  paragraph 12 below.  If Buyer does not  exercise the Option,  Buyer
shall  deliver  possession  of the Real  Property  Assets in the same  condition
existing on the date of complete  execution  hereof,  except for normal wear and
tear, and Quest shall be responsible for any damage to such Real Property Assets
caused by Quest.  In the event of any loss,  damage or  destruction  to the Real
Property Assets occurring prior to such conveyance  (other than damage caused by
Quest),  Quest may elect (i) to refuse to purchase any item of the Real Property
Assets so damaged or (ii) to close the transaction  without regard to such loss,
damage or destruction but with an mutually-agreed upon reduction in the purchase
price.  If the  parties  are  unable to agree  upon such  adjustment,  then such
dispute shall be resolved by arbitration as provided in paragraph 11 below.

         10. ENTIRE AGREEMENT.  This Agreement  contains the entire agreement of
the parties  hereto  with  respect to the subject  matter  hereof,  and no prior
agreement or understanding  pertaining to any such matter shall be effective for
any  purpose.  No  provision

                                      -48-
<PAGE>

hereof may be amended  except by an agreement  in writing  signed by the parties
hereto or their respective successors in interest.

         11.  ARBITRATION.  The arbitration  provisions of Section 11. 11 of the
Asset Purchase Agreement are hereby  incorporated  herein as if freely set forth
in this paragraph 11.

         12. REPURCHASE OF REAL PROPERTY ASSETS.

         (a)  Conveyance.  In the event that Buyer does not exercise the Option,
then on the  date  of  termination  of the  Lease  (the  "Real  Property  Assets
Closing"),  the Buyer shall sell,  transfer  and convey to Quest and Quest shall
purchase from the Buyer, the Real Property Assets,  free and clear of all liens,
mortgages  and  encumbrances,  for the  purchase  price  and upon the  terms and
conditions set forth below. The Real Property Assets Closing shall take place at
the offices located at the Property.

         (b) Purchase  Price.  The purchase price for Real Property Assets shall
be their Net Book  Value,  as defined on  Exhibit B attached  hereto,  as of the
[insert  date which is nine months  following  the Closing  Date under the Asset
Purchase Agreement].

         (c) Delivery at Closing.  At the Real Property  Assets Closing and as a
condition  precedent  thereto,  the Buyer  shall  deliver a bill of sale and any
other documents necessary to convey the Real Property Assets to Quest.

         (d)  Prorations.  All ad valorem  taxes  relating to the Real  Property
Assets shall be prorated as of the date of the Real Property Assets Closing.

         (e)  Remedies.  In the event that Quest  defaults in its  obligation to
repurchase the Real Property  Assets,  then Buyer may take possession and remove
all the Real  Property  Assets  from the  Property,  in  addition  to any  other
remedies available to Buyer at law or equity.

                                      -49-
<PAGE>

         IN WITNESS  WHEREOF,  Buyer and Quest have executed and delivered  this
Agreement as of the day and year first above written.

                                          QUEST MEDICAL, INC.

                                          By:   /s/ F. Robert Merrill
                                                ------------------------------

                                          Its:  Senior Vice President Finance
                                                ------------------------------

                                          QMI MEDICAL, INC.

                                          By:   /s/ Jerry A. Howard
                                                ------------------------------

                                          Its:  President
                                                ------------------------------

                                      -50-
<PAGE>

STATE OF TEXAS                      )
         Collin             COUNTY  )
---------------------------

Before me, Marta  Kennedy , on this day  personally  appeared F. Robert  Merrill
known  to me to be  the  person  whose  name  is  subscribed  to  the  foregoing
instrument,  and known to me to be the Senior  Vice  President  Finance of Quest
Medical, Inc., a Texas corporation,  and acknowledged to me that he/she executed
said instrument for the purposes and consideration therein expressed, and as the
act of said  corporation.  Given under my hand and seal of office this 30 day of
January ,1998.

                                                     /s/ Marta Kennedy
                                                 -----------------------------
                                                 NOTARY PUBLIC

                                                 MY COMMISSION EXPIRES: 8-15-01
                                                                        -------

STATE OF TEXAS                      )
         Collin            COUNTY   )
---------------------------

Before me, Marta  Kennedy , on this day  personally  appeared  Jerry A. Howard ,
known  to me to be  the  person  whose  name  is  subscribed  to  the  foregoing
instrument,  and known to me to be the  President of QMI Medical,  Inc., a Texas
corporation,  and  acknowledged  to me that he executed said  instrument for the
purposes  and  consideration   therein  expressed,   and  as  the  act  of  said
corporation.  Given  under my hand and seal of office  this 30 day of  January ,
1998.

                                                    /s/ Marta Kennedy
                                                 -------------------------------
                                                 NOTARY PUBLIC

                                                 MY COMMISSION EXPIRES: 8-15-01
                                                                        -------

                                      -51-

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