Exhibit 10.13

                       [ WILCOX LOGO APPEARS HERE ]


  August 12 1994

  Mr. Robert Brown. CFPIM
  Director of Materials Management
  Carrington Laboratories, Inc.
  2001 Walnut Hill Lane
  Irving, TX 75038

  Re:  Lease Agreement  Between  DFW  Nine,  as  Lessor,  and  Carrington
       Laboratories, Inc.,  as Lessee,  for  Leased Premises  located  at
       1909 Hereford Drive, Irving, Texas.

  Dear Robert:

  This letter serves  to (i) Amend  the Commencement Date  to August  15,
  1994, and (ii)  Confirm that  the Leased  Premises were  leased to  the
  Lessee an lessee accepts the Leased  Premises "as is" except for  those
  items specifically  referenced  in  the Lease  Agreement  &  Exhibit  A
  attached hereto.

  Kindly confirm Carrington Laboratories,  Inc.'s agreement of the  above
  by having  the  appropriate  party  sign  below  and  return  four  (4)
  counterparts of this letter to me.  I will then present the letter  for
  Lessor's signature and return a fully executed copy to you.


  Sincerely,

  WILCOX REALTY GROUP, INC.

  /S/
  James T. Hancock
  Vice President - Marketing
  JTH/jks
  Enclosures


  AGREED AND ACCEPTED;
  LESSEE:  Carrington Laboratories, Inc.

  BY:   /S/
     -----------------------------------
  NAME: ________________________________
  TITLE:________________________________
  DATE: ________________________________


  LESSOR:-DFW Nine, a California limited partnership

  BY:  Meridian Point Properties, Inc.

  BY:   /S/
     -----------------------------------
  NAME: ________________________________
  TITLE:________________________________
  DATE: ________________________________

<PAGE>


                                EXHIBIT "A"


  August 10, 1994


  Mr. Steve Belken
  Univera
  4250 North Beltline Road
  Irving, Texas 75038


  RE:  1909 Hereford

   Dear Steve:


  The following  details the  estimated costs  associated with  necessary
  repairs  and  maintenance  required  to  be  completed  as  the   above
  referenced property in accordance with your Lease Agreement:

                                               Not to Exceed Costs
  DESCRIPTION                                    (including tax)
  -----------                                    ---------------
  HVAC
  Repairs & Maintenance per Griffin                 $9,525.00
  Mechanical's attached inspection
  report dated July 29, 1994.

  ELECTRICAL
  Replacement of extinguished light                 $2,108.00
  bulbs, ballasts, and fire exit
  lamps per Hugh Carrington's notes
  dated July 25, 1994 and Amber Electric's
  attached proposal dated August 4, 1994.

  DOCK DOORS & SHELTER
  Dock door repairs shown as item (A)               $569.00
  on attached proposal from Overhead Door
  Company dated August 2, 1994.


  Replace one dock shelter shown as item            $1,055.00
  (C.2) on attached proposal from Overhead
  Door Company dated August 2, 1994.

  Dock levellers repairs                            Unknown


  WAREHOUSE
  Water cooler replacement                          Unknown
  Floor cleaning (fork lift marks & oil spills)     Unknown
  Chain link fence replacement                      Unknown
<PAGE>
  CARPETING
  Bleached place in corner office                   Unknown
  Large tear in open office area
  2 small offices by lab area (including
  cove base)

  WINDOW GLAZING
  Repair Leaks in the conference room


  Due to the  Landlord's leniency  to date  on enforcement  of this  work
  which should have been completed prior to July 31, 1994, our assistance
  in obtaining  cost  estimates  for  this  work  which  is  your  firm's
  responsibility, and the fact that we have not demanded a rental payment
  for August  to  date,  we respectfully  request  your  cooperation  and
  fairness in regards to the above items  for which a repair cost is  not
  known at  this time.  We currently  retain a  security deposit  in  the
  amount of  $6,500  which  can  be  applied  towards  these  repair  and
  maintenance costs.

  Steve, we certainly intend  to be fair and  reasonable in terms of  the
  scope of work for  remaining items and  their associated costs.  Please
  sign below as your acknowledgement and approval for us to proceed  with
  the  HVAC,  electrical,  dock  door  repairs,  and  one  dock   shelter
  replacement. These  costs  are  Univera's  responsibility  and  Univera
  agrees to reimburse the Landlord accordingly.

  I will obtain the needed information on the pending cost estimates  and
  advise you  immediately. Please  feel  free to  call  if you  have  any
  questions.

  Sincerely,

  WILCOX REALTY GROUP            ACCEPTED:

  /s/                            __________________________________

  Louann Davison                 DATE:
  Property Manager

                                 __________________________________
  LD/jh

  cc:  Jim Hancock