SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13G
                                 (Rule 13d-102)

           INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO
    RULES 13d-1(b)(c), AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO RULE
                                    13d-2(b)
                               (Amendment No. _)1

                           MacroPore Biosurgery, Inc.
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                                (Name of Issuer)

                          Common Stock, $.001 par value
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                         (Title of Class of Securities)

                                   U55396 10 2
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                                 (CUSIP Number)

                                February 8, 2005
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             (Date of Event Which Requires Filing of this Statement)


Check  appropriate  box to designate the rule pursuant to which this Schedule is
filed:


  [ ] Rule 13d-1(b)

  [X] Rule 13d-1(c)

  [ ] Rule 13d-1(d)



     1The  remainder  of this cover  page  shall be filled  out for a  reporting
person's  initial  filing on this  form with  respect  to the  subject  class of
securities,  and for any subsequent amendment containing information which would
alter the disclosures provided in a prior cover page.

     The  information  required in the remainder of this cover page shall not be
deemed to be "filed"  for the purpose of Section 18 of the  Securities  Exchange
Act of 1934 ("Act") or otherwise  subject to the  liabilities of that section of
the Act but shall be subject to all other  provisions of the Act  (however,  see
the Notes).





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CUSIP NO. U55396 10 2                       Page  2  of  6   Pages
          -----------                             --     -        
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1                              NAME OF REPORTING PERSON
                               S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE
                               PERSON (ENTITIES ONLY)

                               Neil Gagnon
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2                              CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                   (a) [ ]
                                                                   (b) [X]
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3                              SEC USE ONLY

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4                              CITIZENSHIP OR PLACE OF ORGANIZATION

                               United States of America
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                       5       SOLE VOTING POWER

                               200,859
                       ---------------------------------------------------------
      NUMBER OF        6       SHARED VOTING POWER
       SHARES
    BENEFICIALLY               117,605
      OWNED BY         ---------------------------------------------------------
        EACH           7       SOLE DISPOSITIVE POWER
      REPORTING
       PERSON                  179,845
        WITH           ---------------------------------------------------------
                       8       SHARED DISPOSITIVE POWER

                               606,441
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9                      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH
                       REPORTING PERSON

                       786,286
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10                     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES
                       CERTAIN SHARES* [ ]
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PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

                       5.6%
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--------------------------------------------------------------------------------
12                     TYPE OF REPORTING PERSON*

                       IN
--------------------------------------------------------------------------------

                      *SEE INSTRUCTION BEFORE FILLING OUT!





Item 1(a)   Name of Issuer:

         MacroPore Biosurgery, Inc.

Item 1(b)   Address of Issuer's Principal Executive Offices:

         6740 Top Gun Street
         San Diego, CA 92121

Item 2(a)   Name of Person Filing:

         Neil Gagnon

Item 2(b)   Address of Principal Business Office or, if none, Residence:

         1370 Avenue of the Americas
         Suite 2002
         New York, NY 10019

Item 2(c)   Citizenship:

         United States of America

Item 2(d)   Title of Class of Securities:

         Common Shares, par value $.001 per share

Item 2(e)    CUSIP Number:

         U55396 10 2

Item 3      Type of Reporting Person:

         Not Applicable

Item 4       Ownership.

Item 4(a)   Amount Beneficially Owned:

     As of February 8, 2005,  Neil Gagnon  beneficially  owned 786,286 shares of
Common Stock of MacroPore  Biosurgery,  Inc.,  which amount includes (i) 111,015
shares  beneficially  owned by Mr. Gagnon over which he has sole voting and sole
dispositive  power;  (ii) 20,249  shares  beneficially  owned by Mr. Gagnon over
which he has sole  voting and shared  dispositive  power;  (iii)  68,780  shares
beneficially  owned by Lois Gagnon,  Mr. Gagnon's wife, over which he has shared
voting and shared  dispositive power; (iv) 24,480 shares held by the Lois E. and
Neil E. Gagnon Foundation



(the  "Foundation") (of which Mr. Gagnon is a trustee) over which Mr. Gagnon has
shared voting and shared dispositive power; (v) 24,345 shares held by the Gagnon
Family  Limited  Partnership  (the  "Partnership")  (of  which  Mr.  Gagnon is a
partner) over which Mr. Gagnon has shared voting and shared  dispositive  power;
(vi) 20,060  shares held by the Gagnon  Grandchildren  Trust (the  "Trust") over
which Mr. Gagnon has shared dispositive but no voting power; (vii) 66,690 shares
held by a hedge  fund (of which  Mr.  Gagnon is the  principal)  over  which Mr.
Gagnon has sole voting and sole dispositive  power;  (viii) 2,140 shares held by
the  Gagnon  Securities  LLC P/S Plan (the  "Plan")  (of  which Mr.  Gagnon is a
trustee) over which Mr. Gagnon has sole voting and sole dispositive  power; (ix)
765  shares  held by the Plan over which Mr.  Gagnon has sole  voting and shared
dispositive  power; and (x) 447,762 shares held for certain  customers of Gagnon
Securities  LLC (of which Mr.  Gagnon is the Managing  Member and the  principal
owner) over which shares Mr. Gagnon has shared dispositive but no voting power.

Item 4(b)   Percent of Class:

     5.6%  beneficially  owned  by Mr.  Gagnon.  Calculation  of  percentage  of
beneficial  ownership  is based on  13,927,184  shares of Issuer's  Common Stock
outstanding  as of October 25,  2004 as reported by the Issuer in its  Quarterly
Report filed on Form 10-Q for the period ended September 30, 2004.

Item 4(c)   Number of shares as to which such person has:

          (i) sole power to vote or to direct the vote: 200,859

          (ii) shared power to vote or to direct the vote: 117,605

          (iii) sole power to dispose or to direct the disposition of: 179,845

          (iv) shared power to dispose or to direct the disposition of: 606,441

Items 5-9.  Not applicable.

     Filing of this  statement  by the  Reporting  Person shall not be deemed an
admission that he  beneficially  owns the securities  reported herein as held in
customer accounts at Gagnon Securities LLC, by the Foundation,  the Partnership,
the Trust or the Plan. Mr. Gagnon expressly  disclaims  beneficial  ownership of
all  securities  held  in  such  customer  accounts  or by the  Foundation,  the
Partnership,  the Trust or the Plan. No single client's  interest as reported in
the customer  accounts at Gagnon  Securities  LLC exceeds 5% of the  outstanding
Common Stock.

Item 10     Certification.

     By signing  below I certify  that,  to the best of my knowledge and belief,
the  securities  referred  to above were not  acquired  and are not held for the
purpose of or with the effect of  changing  or  influencing  the  control of the
issuer of the  securities  and were not acquired and are not held in  connection
with or as a participant in any transaction having that purpose or effect.





                                    SIGNATURE

     After  reasonable  inquiry and to the best of my  knowledge  and belief,  I
certify that the information  set forth in this statement is true,  complete and
correct.

                                                    March 2, 2005
                                                    ----------------------
                                                    Date


                                                    /s/ Neil Gagnon
                                                    ----------------------
                                                    Neil Gagnon