Exhibit 24



                                POWER OF ATTORNEY
                         FOR EXECUTING FORMS 3, 4 AND 5

       Know all by these presents, that the undersigned hereby constitutes and
appoints each of Peter J. Beshar, Bart Schwartz and Leon J. Lichter, signing
singly, his true and lawful attorney-in-fact to:

       (1)    execute for and on behalf of the undersigned Forms 3, 4 and 5 in
              accordance with Section 16(a) of the Securities Exchange Act of
              1934 and the rules thereunder;

       (2)    do and perform any and all acts for and on behalf of the
              undersigned which may be necessary or desirable to complete the
              execution of any such Form 3, 4 or 5 and the timely filing of such
              form with the United States Securities and Exchange Commission and
              any other authority; and

       (3)    take any other action of any type whatsoever in connection with
              the foregoing which, in the opinion of such attorney-in-fact, may
              be of benefit to, in the best interest of, or legally required by,
              the undersigned, it being understood that the documents executed
              by such attorney-in-fact on behalf of the undersigned pursuant to
              this Power of Attorney shall be in such form and shall contain
              such terms and conditions as such attorney-in-fact may approve in
              his discretion.

       The undersigned hereby grants to each such attorney-in-fact full power
and authority to do and perform each and every act and thing whatsoever
requisite, necessary and proper to be done in the exercise of any of the rights
and powers herein granted, as fully to all intents and purposes as the
undersigned might or could do if personally present, with full power of
substitution or revocation, hereby ratifying and confirming all that such
attorney-in-fact, or his substitute or substitutes, shall lawfully do or cause
to be done by virtue of this Power of Attorney and the rights and powers herein
granted. The undersigned acknowledges that the foregoing attorneys-in-fact, in
serving in such capacity at the request of the undersigned, are not assuming any
of the undersigned's responsibilities to comply with Section 16 of the
Securities Exchange Act of 1934. This authorization shall remain in effect
unless and until it is revoked in writing by the undersigned.

       IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of this 16th day of May, 2005.


                                               /s/ Mathis Cabiallavetta
                                               ---------------------------------
                                               Mathis Cabiallavetta