EXHIBIT 24.3
 
                               POWER OF ATTORNEY
 
  KNOWN ALL MEN BY THESE PRESENTS, that the undersigned hereby constitutes and
appoints each of David C. Flaugh, James G. Richmond and Joram C. Salig or any
of them, each acting alone, his true and lawful attorney-in-fact and agent,
with full power of substitution, for him and in his name, place and stead, in
any and all capacities, in connection with the National Health Laboratories
Holdings Inc. (the "Corporation") registration statement on Form S-4/S-3 (or
any separate registration statements on Forms S-4 and S-3) (the "Registration
Statement") under the Securities Act of 1933, as amended, including, without
limiting the generality of the foregoing, to sign the Registration Statement
in the name and on behalf of the Corporation or on behalf of the undersigned
as a director or officer of the Corporation, and any amendments (including
post-effective amendments) to the Registration Statement (whether on Form S-4
or S-3) and any instrument, contract, document or other writing, of or in
connection with the Registration Statement or amendments thereto, and to file
the same, with all exhibits thereto, and other documents in connection
therewith, including this power of attorney, with the Securities and Exchange
Commission and any applicable securities exchange or securities self-
regulatory body, granting unto said attorneys-in-fact and agents, each acting
alone, full power and authority to do and perform each and every act and thing
requisite and necessary to be done in and about the premises, as fully to all
intents and purposes as he might or could do in person, hereby ratifying and
conforming all that said attorneys-in-fact and agents, each acting alone, or
his substitute or substitutes, may lawfully do or cause to be done by virtue
hereof.
 
  IN WITNESS WHEREOF, the undersigned has signed these presents this 20th day
of February 1995.
 
                                                /s/ Saul J. Farber, M.D.
                                          ---------------------------------
                                                  SAUL J. FARBER, M.D.