<PAGE>   1
                                                                Exhibit 10.26



                            DEXTERITY SURGICAL, INC.




                 SERIES C CUMULATIVE CONVERTIBLE PREFERRED STOCK

                               PURCHASE AGREEMENT



                                  JULY 31, 2000

<PAGE>   2



                 SERIES C CUMULATIVE CONVERTIBLE PREFERRED STOCK
                               PURCHASE AGREEMENT


         This AGREEMENT (the "Agreement"), dated as of July 31, 2000, is entered
into by and among DEXTERITY SURGICAL, INC., a Delaware corporation (the
"Company"), TFX EQUITIES, INC. (together with any permitted assignees or
successors, the "Purchaser").

                                     RECITAL

         WHEREAS, the Purchaser desires to purchase 300 shares of Series C
Cumulative Convertible Preferred Stock, par value $.001 per share, of the
Company (the "Series C Preferred Stock"), having the rights, preferences,
privileges and restrictions set forth in the Company's Certificate of
Designation and Preferences of Series C Cumulative Convertible Preferred Stock
by resolution, substantially in the form attached hereto as EXHIBIT A (the
"Certificate of Designation"), and the Company desires to sell to the Purchaser
such shares of Series C Preferred Stock on the terms and subject to the
conditions set forth herein;

                                    AGREEMENT

         NOW, THEREFORE, in consideration of the premises, mutual covenants and
agreements hereinafter contained and for other good and valuable consideration,
the Company and the Purchaser hereby agree as follows:

                          ARTICLE I - PURCHASE AND SALE

         Section 1.1 PURCHASE AND SALE; PURCHASE PRICE. Subject to the
provisions of this Agreement, at Closing (as hereinafter defined), the Company
shall sell to the Purchaser and the Purchaser shall purchase from the Company
300 shares of Series C Preferred Stock at the purchase price of $300,000 (the
"Purchase Price").

         Section 1.2 CLOSING. The purchase and sale of the Series C Preferred
Stock pursuant to Section 1.1 (the "Closing") shall take place at the offices of
Fulbright & Jaworski, L.L.P., 300 Convent, Suite 2200, San Antonio, Texas 78205
or at such other place as may be agreed upon by the Company and the Purchaser,
at 10:00 a.m., local time, on July 31, 2000, or at such other time and date as
may be agreed upon by the Company and the Purchaser (the "Closing Date").

         Section 1.3 TRANSACTIONS AT CLOSING. At the Closing, the Company shall
deliver to the Purchaser a certificate for the shares of Series C Preferred
Stock to be issued and sold to the Purchaser hereunder duly registered in the
Purchaser's name, or in such other name as the Purchaser shall have specified in
writing to the Company, against payment in full by the Purchaser of the Purchase
Price by wire transfer of immediately available funds.


<PAGE>   3



           ARTICLE II - REPRESENTATIONS AND WARRANTIES OF THE COMPANY

         The Company represents and warrants to the Purchaser that:

         Section 2.1 CAPITALIZATION. On the Closing Date, the authorized capital
stock of the Company shall consist of (a) 2,000,000 shares of preferred stock,
par value $.001 per share, of which (i) 1,170 shares are designated "Series A
Cumulative Convertible Preferred Stock" and of which 1,170 shares have been
issued and 1,020 are outstanding, (ii) 1,025 shares are designated "Series B
Cumulative Convertible Preferred Stock" of which 1,025 shares are issued and
outstanding and (iii) 1,000 shares will be designated "Series C Cumulative
Convertible Preferred Stock" of which no shares will be issued and outstanding
prior to the Closing Date and (b) 50,000,000 shares of common stock, par value
$.001 per share (the "Common Stock"), of which 11,496,492 shares are issued and
outstanding, a total of 6,459,100 shares are reserved for issuance pursuant to
outstanding options, warrants and debentures, 653,846 shares are reserved for
issuance upon conversion of the Series A Cumulative Convertible Preferred Stock,
657,051 shares are reserved for issuance upon conversion of the Series B
Preferred Cumulative Convertible Stock and 1,000,000 shares are reserved for
issuance upon conversion of the Series C Preferred Stock. The outstanding shares
of Common Stock are duly authorized and validly issued, fully paid and
nonassessable and not subject to preemptive rights. Holders of shares of the
Company's capital stock have no preemptive rights or rights of first refusal.

         Section 2.2 VALIDITY OF STOCK. The Series C Preferred Stock, when
issued, sold and delivered in accordance with the terms of this Agreement, will
be duly authorized and validly issued, fully paid and nonassessable, and will be
free of restrictions on transfer, other than restrictions on transfer under
applicable state and federal securities laws, and not subject to preemptive
rights. The Common Stock issuable upon conversion of the Series C Preferred
Stock purchased under this Agreement has been duly and validly reserved for
issuance and, upon issuance in accordance with the terms of the Certification of
Designation, will be duly and validly issued, fully paid, and nonassessable and
will be free of restrictions on transfer other than restrictions on transfer
under applicable state and federal securities laws.

         Section 2.3 AUTHORIZATION; APPROVALS. All corporate action on the part
of the Company and its stockholders necessary for the authorization, execution,
delivery and performance of all its obligations under this Agreement and for the
authorization, issuance and delivery of the Series C Preferred Stock being sold
under this Agreement and of the Common Stock initially issuable upon conversion
of the Series C Preferred Stock has been (or will be) taken prior to the
Closing. This Agreement, when executed and delivered by or on behalf of the
Company, shall constitute the valid and binding obligation of the Company,
enforceable against the Company in accordance with its terms. The Company has
obtained or will obtain prior to the Closing Date all necessary consents,
authorizations, approvals and orders, and has made all registrations,
qualifications, designations, declarations or filings with all federal, state or
other relevant governmental authorities required on the part of the Company in
connection with the consummation of the transactions contemplated by this
Agreement, except for such filings as may be required to be made after the
Closing in order to comply with the requirements of Regulation D promulgated
under the Securities Act of 1933, as amended (the "Securities Act") and
applicable state laws.

                                        2

<PAGE>   4



         Section 2.4 SEC REPORTS. The Company has filed all reports,
registration or proxy statements, forms and documents with the SEC that it was
required to file since the date of the initial public offering of its Common
Stock (the "SEC Filings"), all of which have complied in all material respects
with all applicable requirements of the Securities Act and the Exchange Act. As
of their respective dates, each of the SEC Filings, including, without
limitation, any financial statements or schedules included therein, did not
contain any untrue statement of a material fact or omit to state a material fact
required to be stated therein or necessary to make the statements therein, in
light of the circumstances under which they were made, not misleading.

         ARTICLE III - REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE
                                    PURCHASER

         The Purchaser represents and warrants to the Company that:

         Section 3.1 AUTHORIZATION; APPROVALS; NO CONFLICTS. This Agreement,
when executed and delivered by the Purchaser shall constitute the valid and
binding obligation of the Purchaser, enforceable against the Purchaser in
accordance with its terms. The Purchaser has obtained or will obtain prior to
the Closing Date all necessary consents, authorizations, approvals and orders,
and have made all registrations, qualifications, designations, declarations or
filings with all federal, state or other relevant governmental authorities
required on the part of the Purchaser in connection with the consummation of the
transactions contemplated by this Agreement. The execution, delivery and
performance of this Agreement will not result in any violation of, be in
conflict with, or constitute, with or without the passage of time or giving of
notice or both, a default under any terms or provisions of (i) any judgment,
decree or order of any court or government agency or body having jurisdiction
over the Purchaser or his properties; (ii) any agreement, contract,
understanding, indenture or other instrument to which the Purchaser is a party
or by which the Purchaser is bound, the effect of which would have a material
adverse effect on the assets, properties, condition (financial or otherwise),
operating results, prospects or business of the Purchaser; or (iii) any statute,
rule or governmental regulation applicable to the Purchaser.

         Section 3.2 INVESTMENT REPRESENTATIONS. The Purchaser is acquiring the
Series C Preferred Stock (and any Common Stock into which the Series C Preferred
Stock may be converted) for the Purchaser's own account, for investment purposes
and not with a view to, or for sale in connection with, any distribution of such
shares.

         Section 3.3 INVESTMENT EXPERIENCE; ACCESS TO INFORMATION. The Purchaser
is an "accredited investor," as that term is defined in Rule 501(a) promulgated
under the Securities Act. The Purchaser has been afforded prior to the Closing
Date the opportunity to ask questions of, and to receive answers from, the
Company and to obtain any additional information, written and oral, to the
extent the Company has such information or could have acquired it without
unreasonable effort or expense, all as necessary for the Purchaser to make an
informed investment decision with respect to the purchase of the Series C
Preferred Stock.

         Section 3.4 RESTRICTIONS ON TRANSFER. The Purchaser agrees that (a) the
Purchaser will not offer, sell, transfer, give, pledge, hypothecate or otherwise
dispose of the Series C Preferred


                                        3

<PAGE>   5



Stock (or the Common Stock into which it may be converted) or make any attempt
to do the foregoing unless such offer, sale, transfer, gift, pledge,
hypothecation or other disposition is (i) registered under the Securities Act
and any applicable state securities law, or (ii) in compliance with an opinion
of counsel to the Purchaser, delivered to the Company and reasonably acceptable
to counsel for the Company, to the effect that such offer, sale, pledge,
hypothecation or other disposition thereof does not violate the Securities Act
or applicable state securities law, and (b) the certificate(s) representing the
Series C Preferred Stock (and any Common Stock into which it may be converted)
shall bear a legend stating in substance:

                  THE SECURITIES REPRESENTED BY THIS CERTIFICATE
                  HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
                  ACT OF 1933, AS AMENDED (THE "ACT"), OR UNDER
                  ANY APPLICABLE STATE SECURITIES LAWS AND ARE
                  "RESTRICTED SECURITIES" AS THAT TERM IS DEFINED
                  IN RULE 144 UNDER THE ACT. NEITHER THE SHARES
                  NOR ANY INTEREST THEREIN MAY BE OFFERED FOR
                  SALE, SOLD, TRANSFERRED, PLEDGED OR OTHERWISE
                  DISPOSED OF EXCEPT PURSUANT TO AN EFFECTIVE
                  REGISTRATION STATEMENT UNDER THE ACT AND SUCH
                  STATE SECURITIES LAWS OR AN EXEMPTION FROM
                  REGISTRATION UNDER SUCH ACT AND SUCH LAWS
                  WHICH, IN THE OPINION OF COUNSEL FOR THE
                  HOLDER, WHICH COUNSEL AND OPINION ARE
                  REASONABLY SATISFACTORY TO THE COUNSEL FOR THIS
                  CORPORATION, IS AVAILABLE.

         Upon request of a holder of Series C Preferred Stock (or the Common
Stock into which it has been converted), the Company shall remove the legend set
forth above from the certificates evidencing such Series C Preferred Stock or
Common Stock or issue to such holder new certificates therefor free of such
legend, if with such request the Company shall have received an opinion of
counsel selected by the holder and reasonably satisfactory to the Company, in
form and substance reasonably satisfactory to the Company, to the effect that
such Series C Preferred Stock or Common Stock is not required by the Securities
Act to continue to bear the legend.

         Section 3.5 TRANSFER INSTRUCTIONS. The Purchaser agrees that the
Company may provide for appropriate transfer instructions to implement the
provisions of Section 3.4 hereof.

         Section 3.6 FEES AND COMMISSIONS. The Purchaser has retained not any
finder, broker, agent, financial advisor or other intermediary in connection
with the transactions contemplated by this Agreement, and the Purchaser agrees
to indemnify and hold harmless the Company from liability for any compensation
to any such finder, broker, agent, financial advisor or other intermediary and
the fees and expenses of defending against such liability or alleged liability.


                                        4

<PAGE>   6



               ARTICLE IV - CONDITIONS TO CLOSING OF THE PURCHASER

         The obligation of the Purchaser on the Closing Date to purchase the
Series C Preferred Stock shall be subject to each of the following conditions
precedent, any one or more of which may be waived by the Purchaser:

                  (a) REPRESENTATIONS AND WARRANTIES. The representations and
warranties made by the Company herein shall be true and accurate in all material
respects on and as of the Closing Date as if made on the Closing Date.

                  (b) PERFORMANCE. The Company shall have performed and complied
with all agreements and conditions contained herein and other documents incident
to the transactions contemplated by this Agreement required to be performed or
complied with by it prior to or at the Closing.

                  (c) CONSENTS. The Company shall have secured all permits,
consents and authorizations that shall be necessary or required lawfully to
consummate the transactions contemplated by this Agreement, to issue the Series
C Preferred Stock to be purchased by the Purchaser and to issue the Common Stock
into which the Series C Preferred Stock may be converted.

                  (d) COMPLIANCE CERTIFICATES. The Company shall have delivered
to the Purchaser or his representative at the Closing an Officer's Certificate
to the effect that all conditions specified in subsections (a) to (c),
inclusive, have been fulfilled.

                  (e) CERTIFICATE OF DESIGNATION. The Certificate of Designation
shall have been duly filed with the Secretary of State of the State of Delaware.

                ARTICLE V - CONDITIONS TO CLOSING OF THE COMPANY

         The obligation of the Company on the Closing Date to issue and sell the
Series C Preferred Stock to be purchased under this Agreement shall be subject
to the representations and warranties made by the Purchaser herein being true
and accurate on and as of such Closing Date.

                           ARTICLE VI - MISCELLANEOUS

         Section 6.1 ENTIRE AGREEMENT. This Agreement constitutes the entire
agreement between the parties hereto and supersedes all prior agreements and
understandings, oral and written, between the parties hereto with respect to the
subject matter hereof. No party shall be liable or bound to any other party in
any manner by any warranties, representation, or covenants except as
specifically set forth herein or therein.

         Section 6.2 SURVIVAL OF REPRESENTATIONS AND WARRANTIES. The warranties,
representations and covenants of the Company and the Purchaser contained in or
made pursuant to this Agreement shall survive the execution and delivery of this
Agreement and the Closing.


                                        5

<PAGE>   7



         Section 6.3 NOTICES. All notices, requests, demands, consents and other
communications herein shall be in writing and shall be deemed, unless otherwise
specified herein, to have been duly given if personally delivered or mailed,
first-class certified mail, postage prepaid and return receipt requested or sent
by recognized overnight courier service or transmitted by telex or facsimile, as
follows:

                  (a)    If to the Company:

                         Dexterity Surgical, Inc.
                         12961 Park Central, Suite 1300
                         San Antonio, Texas  78216
                         Attention: Chief Financial Officer
                         Facsimile number: (210) 495-4441

                         with a copy to (which shall not constitute
                         effective notice to the Company):

                         Fulbright & Jaworski L.L.P.
                         300 Convent Street, Suite 2200
                         San Antonio, Texas  78205
                         Attention:  Phillip M. Renfro, Esq.
                         Facsimile number:  (210) 270-7205

                  (b)    If to Purchaser:

                         TFX Equities, Inc.
                         1787 Sentry Parkway West
                         Building Sixteen, Suite 220
                         Blue Bell, Pennsylvania  19422
                         Attention:  John J. Sickler, President
                         Facsimile number: (___) ____-______

or such other addresses as either of the parties hereto may provide from time to
time in writing to the other party. For purposes of computing the time periods
set forth in this Section 6.3, the delivery date shall be deemed to be (i) three
(3) days after the date of mailing, (ii) the date personally delivered or sent
by telex or facsimile, or (iii) the business day after the date sent by
recognized overnight courier service.

         Section 6.4 AMENDMENTS. Any term of this Agreement may be amended only
with the written consent of the Company and the holders of the Series C
Preferred Convertible Stock not previously sold to the public. Any amendment
effected in accordance with this paragraph shall be binding upon each holder of
Series C Preferred Stock purchased under this Agreement at the time outstanding
(including Common Stock into which such Series C Preferred Stock have been
converted), each future holder of such securities, and the Company.



                                        6

<PAGE>   8



         Section 6.5 WAIVER AND CONSENT. No action taken pursuant to this
Agreement, including any investigation by or on behalf of either party, shall be
deemed to constitute a waiver by the party taking such action of compliance with
the other party hereto or a breach of any representations, warranties, covenants
or agreements contained herein. The waiver by either party hereto of a breach of
any provision of this Agreement shall not operate or be construed as a waiver of
any preceding or succeeding breach, and no failure by either party to exercise
any right or privilege hereunder shall be deemed a waiver of such party's rights
or privileges hereunder or shall be deemed a waiver of such party's rights to
exercise the same at any subsequent time or times hereunder.

         Section 6.6 SUCCESSORS AND ASSIGNS. Except as otherwise expressly
provided in this Agreement, all of the terms of this Agreement shall be binding
upon and inure to the benefit of and be enforceable by the respective successors
and assigns of the parties hereto (including permitted transfers of any shares
of Series C Preferred Stock sold hereunder or any Common Stock issued upon
conversion thereof).

         Section 6.7 RIGHTS OF PURCHASER. The Purchaser shall have the absolute
right to exercise or refrain from exercising any right or rights that the
Purchaser may have by reason of this Agreement or any Series C Preferred Stock,
including the right to consent to the waiver of any obligation of the Company
under this Agreement and to enter into any agreement with the Company for the
purpose of modifying this Agreement or any agreement effecting any such
modification.

         Section 6.8 EXECUTION AND COUNTERPARTS. This Agreement may be executed
in any number of counterparts, each of which shall be deemed an original, and
all of which together shall constitute one instrument.

         Section 6.9 NO THIRD PARTY BENEFICIARIES. Except as otherwise provided,
this Agreement has been and is made solely for the benefit of and shall be
binding upon the Company and the Purchaser and no other person shall acquire or
have any rights under or by virtue of this Agreement.

         Section 6.10 SEVERABILITY. Any provision of this Agreement that is
prohibited, unenforceable or not authorized in any jurisdiction shall, as to
such jurisdiction, be ineffective to the extent of such prohibition,
unenforceability or lack of authorization without invalidating the remaining
provisions hereof or affecting the validity, unenforceability or legality of
such provision in any other jurisdiction.

         Section 6.11 GOVERNING LAW. THIS AGREEMENT AND THE LEGAL RELATIONS
AMONG THE PARTIES HERETO SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH
THE LAWS OF THE STATE OF TEXAS, WITHOUT REGARD TO ITS CONFLICTS OF LAW DOCTRINE.

                         [Signatures on following page]



                                        7

<PAGE>   9


         IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the date first above written.

                                        COMPANY:

                                        DEXTERITY SURGICAL, INC.


                                        By:
                                           -------------------------------------
                                           Randall K. Boatright, Executive Vice
                                           President and Chief Financial Officer

                                        PURCHASER:

                                        TFX EQUITIES, INC.


                                        By:
                                           -------------------------------------
                                               John J. Sickler, President