**Exhibit
      4.2**





**STOCK
      PURCHASE WARRANT**


**To
      Purchase Series A Preferred Stock of**





***SPECTRA*** **SCIENCE,
      INC.**





THIS
      WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 (THE “ACT”) NOR
      UNDER ANY STATE SECURITIES LAW AND MAY NOT BE PLEDGED, SOLD, ASSIGNED OR
      OTHERWISE TRANSFERRED UNTIL (1) A REGISTRATION STATEMENT UNDER THE ACT AND
      ANY
      APPLICABLE STATE SECURITIES LAW HAS BECOME EFFECTIVE WITH RESPECT THERETO,
      OR
      (2) RECEIPT BY THE COMPANY OF AN OPINION OF COUNSEL TO THE COMPANY TO THE EFFECT
      THAT REGISTRATION UNDER THE ACT OR APPLICABLE STATE SECURITIES LAW IS NOT
      REQUIRED IN CONNECTION WITH THE PROPOSED TRANSFER.





Void
      after 5:00 p.m. Central Standard Time, on June __, 2012.





**Warrant
      to Purchase 250,000 Shares of Series A Preferred Stock.**


**WARRANT
      TO PURCHASE SERIES A PREFERRED STOCK OF** ***SPECTRA*** **SCIENCE,
      INC.**





This
      is
      to Certify That, FOR VALUE RECEIVED, ___________________ (“Holder”) is entitled
      to purchase, subject to the provisions of this Warrant, from SpectraScience,
      Inc., a Minnesota corporation (“Company”), 250,000 fully paid, validly issued
      and nonassessable shares of Series A Preferred Stock, no par value per share,
      of
      the Company (“Preferred Stock”) at an initial price of $0.50 per share at any
      time or from time to time during the period from the date hereof to 5:00 p.m.
      Central Standard Time, on June __, 2012. The number of shares of Preferred
      Stock
      to be received upon the exercise of this Warrant and the price to be paid for
      each share of Preferred Stock may be adjusted from time to time as hereinafter
      set forth. The exercise price and the number of shares issuable upon exercise
      of
      the Warrants will be proportionately adjusted for stock splits, stock dividends,
      recapitalizations and similar transactions. The shares of Preferred Stock
      deliverable upon such exercise, and as adjusted from time to time, are
      hereinafter sometimes referred to as “Warrant Shares” and the exercise price of
      a share of Preferred Stock in effect at any time and as adjusted from time
      to
      time is hereinafter sometimes referred to as the “Exercise Price”.





(a)  EXERCISE
      OF WARRANT .





(1)  This
      Warrant may be exercised in whole or in part at any time or from time to time
      on
      or after the date hereof and until 5:00 p.m. Central Standard Time on June
      __,
      2012; provided, however, that if either such day is a day on which banking
      institutions in the State of Iowa are authorized by law to close, then on the
      next succeeding day which shall not be such a day. This Warrant may be exercised
      by presentation and surrender hereof to the Company at its principal office
      with
      the Purchase Form annexed hereto duly executed and accompanied by payment of
      the
      Exercise Price for the number of Warrant Shares specified in such form. As
      soon
      as practicable after each such exercise of the warrants, but not later than
      seven (7) days from the date of such exercise, the Company shall issue and
      deliver to the Holder a certificate or certificate for the Warrant Shares
      issuable upon such exercise, registered in the name of the Holder or its
      designee. If this Warrant should be exercised in part only, the Company shall,
      upon surrender of this Warrant for cancellation, execute and deliver a new
      Warrant evidencing the rights of the Holder thereof to purchase the balance
      of
      the Warrant Shares purchasable thereunder. Upon receipt by the Company of this
      Warrant at its office in proper form for exercise, the Holder shall be deemed
      to
      be the holder of record of the shares of Preferred Stock issuable upon such
      exercise, notwithstanding that the stock transfer books of the Company shall
      then be closed or that certificates representing such shares of Preferred Stock
      shall not then be physically delivered to the Holder. In
      lieu
      of delivering the Exercise Price in cash or check the Holder may elect to
      receive shares equal to the value of the Warrant or portion thereof being
      exercised (“Net Issue Exercise”). If the Holder wishes to elect the Net Issue
      Exercise, the Holder shall notify the Company of its election in writing at
      the
      time it delivers to the Company the Purchase Form. In the event the Holder
      shall
      elect Net Issue Exercise, the Holder shall receive the number of shares of
      Preferred Stock equal to the product of (a) the number of shares of Preferred
      Stock purchasable under the Warrant, or portion thereof being exercised, and
      (b)
      the current market value, as defined in paragraph (c), of one share of Preferred
      Stock (or the common stock of the Company that would be received upon the
      conversion of the Preferred Stock) minus the Exercise Price, divided by (c)
      the
      current market value, as defined below, of one share of Preferred Stock (or
      the
      common stock of the Company that would be received upon conversion of the
      preferred stock).




1





(b)  RESERVATION
      OF SHARES .
      The
      Company shall at all times reserve for issuance and/or delivery upon exercise
      of
      this Warrant such number of shares of its Preferred Stock as shall be required
      for issuance and delivery upon exercise of the Warrants.





(c)  FRACTIONAL
      SHARES .
      No
      fractional shares or scrip representing fractional shares shall be issued upon
      the exercise of this Warrant. With respect to any fraction of a share called
      for
      upon any exercise hereof, the Company shall pay to the Holder an amount in
      cash
      equal to such fraction multiplied by the current market value of a share,
      determined as follows:




If
      the
      Preferred Stock (or the common stock of the Company that would be received
      upon
      the conversion of the Preferred Stock) is listed on a national securities
      exchange or admitted to unlisted trading privileges on such exchange or listed
      for trading on the NASDAQ system, the current market value shall be the last
      reported sale price of the Preferred Stock (or common stock) on such exchange
      or
      system on the last business day prior to the date of exercise of this Warrant
      or
      if no such sale is made on such day, the average closing bid and asked prices
      for such day on such exchange or system; or





If
      the
      Preferred Stock (or the common stock of the Company that would be received
      upon
      the conversion of the Preferred Stock) is not so listed or admitted to unlisted
      trading privileges, the current market value shall be the mean of the last
      reported bid and asked prices reported by the National Quotation Bureau, Inc.
      on
      the last business day prior to the date of the exercise of this Warrant;
      or





If
      the
      Preferred Stock (or the common stock of the Company that would be received
      upon
      the conversion of the Preferred Stock) is not so listed or admitted to unlisted
      trading privileges and bid and asked prices are not so reported, the current
      market value shall be an amount, not less than the book value thereof as at
      the
      end of the most recent fiscal year of the Company ending prior to the date
      of
      the exercise of the Warrant, determined in such reasonable manner as may be
      prescribed by the Board of Directors of the Company.





(d)  EXCHANGE,
      TRANSFER, ASSIGNMENT OR LOSS OF WARRANT .
      This
      Warrant is exchangeable, without expense, at the option of the Holder, upon
      presentation and surrender hereof to the Company for other warrants of different
      denominations entitling the holder thereof to purchase in the aggregate the
      same
      number of shares of Preferred Stock purchasable hereunder. Upon surrender of
      this Warrant to the Company at its principal office with the Assignment Form
      annexed hereto duly executed and funds sufficient to pay any transfer tax,
      the
      Company shall, without charge, execute and deliver a new Warrant in the name
      of
      the assignee named in such instrument of assignment and this Warrant shall
      promptly be cancelled. This Warrant may be divided or combined with other
      warrants which carry the same rights upon presentation hereof at the principal
      office of the Company together with a written notice specifying the names and
      denominations in which new Warrants are to be issued and signed by the Holder
      hereof. The term “Warrant” as used herein includes any Warrants into which this
      Warrant may be divided or exchanged. Upon receipt by the Company of evidence
      satisfactory to it of the loss, theft, destruction or mutilation of this
      Warrant, and (in the case of loss, theft or destruction) of reasonably
      satisfactory indemnification, and upon surrender and cancellation of this
      Warrant, if mutilated, the Company will execute and deliver a new Warrant of
      like tenor and date. Any such new Warrant executed and delivered shall
      constitute an additional contractual obligation on the part of the Company,
      whether or not this Warrant so lost, stolen, destroyed, or mutilated shall
      be at
      any time enforceable by anyone.




2





(e)  RIGHTS
      OF THE HOLDER .
      The
      Holder shall not, by virtue hereof, be entitled to any rights of a shareholder
      in the Company, either at law or equity, and the rights of the Holder are
      limited to those expressed in the Warrant and are not enforceable against the
      Company except to the extent set forth herein.





(f)  ANTI-DILUTION
      PROVISIONS .
      The
      Exercise Price in effect at any time and the number and kind of securities
      purchasable upon the exercise of the Warrants shall be subject to adjustment
      from time to time upon the happening of certain events as follows:





(1)  In
      case
      the Company shall (i) declare a dividend or make a distribution on its
      outstanding shares of Common Stock in shares of Common Stock, (ii) subdivide
      or
      reclassify its outstanding shares of Common Stock into a greater number of
      shares, or (iii) combine or reclassify its outstanding shares of Common Stock
      into a smaller number of shares, the Exercise Price in effect at the time of
      the
      record date for such dividend or distribution or of the effective date of such
      subdivision, combination or reclassification shall be adjusted so that the
      Exercise Price shall be proportionately increased (as in the case of (iii),
      above) or decreased (as in the case of (i) or (ii), above). Such adjustment
      shall be made successively whenever any event listed above shall
      occur.





(2)  In
      case
      the Company shall fix a record date for the issuance of rights or warrants
      to
      all holders of its Common Stock entitling them to subscribe for or purchase
      shares of Common Stock (or securities convertible into Common Stock) at a price
      (the “Subscription Price”) (or having a conversion price per share) less than
      the Exercise Price on such record date, the Exercise Price shall be adjusted
      so
      that the same shall equal such lower price. Such adjustment shall be made
      successively whenever such rights or warrants are issued and shall become
      effective immediately after the record date for the determination of
      shareholders entitled to receive such rights or warrants; and to the extent
      that
      shares of Common Stock are not delivered (or securities convertible into Common
      Stock are not delivered) after the expiration of such rights or warrants, the
      Exercise Price shall be readjusted to the Exercise Price which would then be
      in
      effect had the adjustments made upon the issuance of such rights or warrants
      been made upon the basis of delivery of only the number of shares of Common
      Stock (or securities convertible into Common Stock) actually delivered.





(3)  In
      case
      the Company shall hereafter distribute to the holders of its Common Stock
      evidences of its indebtedness or assets (excluding cash dividends or
      distributions and dividends or distributions referred to in Subsection (1)
      above) or subscription rights or warrants (excluding those referred to in
      Subsection (2) above), the Company shall reserve and the holder of this warrant
      shall thereafter, upon exercise hereof, be entitled to receive with respect
      to
      each share of Preferred Stock purchased hereunder, without any change in, or
      payment in addition to Exercise Price, the amount of any property or other
      securities which would have been distributed to such holder had such holder
      been
      a holder of one share of Preferred Stock on the record date of such distribution
      (or, if no record date was established by the Company, the date such
      distribution was paid).





(4)  In
      case
      the Company shall issue shares of its Common Stock excluding shares issued
      (i)
      in any of the transactions described in Subsection (1) above, (ii) upon exercise
      of options granted to the Company’s employees under a plan or plans adopted by
      the Company’s Board of Directors and approved by its shareholders, if such
      shares would otherwise be included in this Subsection (4), (iii) upon exercise
      of this Warrant and (iv) to shareholders of any corporation which merges into
      the Company in proportion to their stock holdings of such corporation
      immediately prior to such merger, upon such merger, or issued in a bona fide
      public offering pursuant to a firm commitment underwriting, but only if no
      adjustment is required pursuant to any other specific subsection of this Section
      (f) (without regard to Subsection (8) below) with respect to the transaction
      giving rise to such rights for a consideration per share (the “Offering Price”)
      less than the Exercise Price, the Exercise Price shall be adjusted immediately
      thereafter so that it shall equal such Offering Price.




Such
      adjustment shall be made successively whenever such an issuance is
      made.




3





(5)  In
      case
      the Company shall issue any securities convertible into or exchangeable for
      its
      Preferred Stock, excluding securities issued in transactions described in
      Subsections (2) and (3) above, for a consideration per share of Preferred Stock
      (the “Conversion Price”) initially deliverable upon conversion or exchange of
      such securities, determined as provided in Subsection (7) below, less than
      the
      Exercise Price, the Exercise Price shall be adjusted immediately thereafter
      so
      that it shall equal such Conversion Price. Such adjustment shall be made
      successively whenever such an issuance is made.





(6)  Whenever
      the Exercise Price payable upon exercise of each Warrant is adjusted pursuant
      to
      Subsections (1), (2), (3), (4) and (5) above, the number of Shares purchasable
      upon exercise of this Warrant shall simultaneously be adjusted by multiplying
      the number of Shares initially issuable upon exercise of this Warrant by the
      Exercise Price in effect on the date hereof and dividing the product so obtained
      by the Exercise Price, as adjusted.





(7)  For
      purposes of any computation respecting consideration received pursuant to
      Subsections (4) and (5) above, the following shall apply:





(A)  In
      the
      case of the issuance of shares of Common Stock for cash, the consideration
      shall
      be the amount of such cash, provided that in no case shall any deduction be
      made
      for any commissions, discounts or other expenses incurred by the Company for
      any
      underwriting of the issue or otherwise in connection therewith;





(B)  In
      the
      case of the issuance of shares of Common Stock for a consideration in whole
      or
      in part other than cash, the consideration other than cash shall be deemed
      to be
      the fair market value thereof as determined in good faith by the Board of
      Directors of the Company (irrespective of the accounting treatment thereof),
      whose determination shall be conclusive; and





(C)  In
      the
      case of the issuance of securities convertible into or exchangeable for shares
      of Common Stock, the aggregate consideration received therefore shall be deemed
      to be the consideration received by the Company for the issuance of such
      securities plus the additional minimum consideration, if any, to be received
      by
      the Company upon the conversion or exchange thereof, the consideration in each
      case to be determined in the same manner as provided in clauses (A) and (B)
      of
      this Subsection (7).





(8)  No
      adjustment in the Exercise Price shall be required unless such adjustment would
      require an increase or decrease of at least two cents ($0.02) in such price;
      provided, however, that any adjustments which by reason of this Subsection
      (8)
      are not required to be made shall be carried forward and taken into account
      in
      any subsequent adjustment required to be made hereunder. All calculations under
      this Section (f) shall be made to the nearest cent or to the nearest
      one-hundredth of a share, as the case may be. Anything in this Section (f)
      to
      the contrary notwithstanding, the Company shall be entitled, but shall not
      be
      required, to make such changes in the Exercise Price, in addition to those
      required by this Section (f), as it shall determine, in its sole discretion,
      to
      be advisable in order that any dividend or distribution in shares of Common
      Stock, or any subdivision, reclassification or combination of Common Stock,
      hereafter made by the Company shall not result in any Federal income tax
      liability to the holders of Common Stock or securities convertible into Common
      or Preferred Stock (including Warrants).





(9)  Whenever
      the Exercise Price is adjusted, as herein provided, the Company shall promptly
      but no later than 20 days after any request for such an adjustment by the
      Holder, cause a notice setting forth the adjusted Exercise Price and adjusted
      number of Shares issuable upon exercise of each Warrant, and, if requested,
      information describing the transactions giving rise to such adjustments, to
      be
      mailed to the Holder at his last address appearing in the Warrant Register,
      and
      shall cause a certified copy thereof to be mailed to its transfer agent, if
      any.
      The Company may retain a firm of independent certified public accountants
      selected by the Board of Directors (who may be the regular accountants employed
      by the Company) to make any computation required by this Section (f), and a
      certificate signed by such firm shall be conclusive evidence of the correctness
      of such adjustment.




4





(10)  In
      the
      event that at any time, as a result of an adjustment made pursuant to Subsection
      (1) above, the Holder of this Warrant thereafter shall become entitled to
      receive any shares of the Company, other than Preferred Stock, thereafter the
      number of such other shares so receivable upon exercise of this Warrant shall
      be
      subject to adjustment from time to time in a manner and on terms as nearly
      equivalent as practicable to the provisions with respect to the Preferred Stock
      contained in Subsections (1) to (8), inclusive above.





(11)  Irrespective
      of any adjustments in the Exercise Price or the number or kind of shares
      purchasable upon exercise of this Warrant, Warrants theretofore or thereafter
      issued may continue to express the same price and number and kind of shares
      as
      are stated in the similar Warrants initially issuable pursuant to this
      Agreement.





(g)  OFFICER’S
      CERTIFICATE .
      Whenever the Exercise Price shall be adjusted as required by the provisions
      of
      the foregoing Section, the Company shall forthwith file in the custody of its
      Secretary or an Assistant Secretary at its principal office an officer’s
      certificate showing the adjusted Exercise Price determined as herein provided,
      setting forth in reasonable detail the facts requiring such adjustment,
      including a statement of the number of additional shares of Preferred Stock,
      if
      any, and such other facts as shall be necessary to show the reason for and
      the
      manner of computing such adjustment. Each such officer’s certificate shall be
      made available at all reasonable times for inspection by the Holder or any
      holder of a Warrant executed and delivered pursuant to Section (a) and the
      Company shall, forthwith after each such adjustment, mail a copy by certified
      mail of such certificate to the Holder or any such holder.





NOTICES
      TO WARRANT HOLDERS .
      So long
      as this Warrant shall be outstanding, (i) if the Company shall pay any dividend
      or make any distribution upon the Common Stock or the Preferred Stock or (ii)
      if
      the Company shall offer to the holders of Common Stock or the Preferred Stock
      for subscription or purchase by them any share of any class or any other rights
      or (iii) if any capital reorganization of the Company, reclassification of
      the
      capital stock of the Company, consolidation or merger of the Company with or
      into another corporation, sale, lease or transfer of all or substantially all
      of
      the property and assets of the Company to another corporation, or voluntary
      or
      involuntary dissolution, liquidation or winding up of the Company shall be
      effected, then in any such case, the Company shall cause to be mailed by
      certified mail to the Holder, at least fifteen days prior to the date specified
      in (x) or (y) below, as the case may be, a notice containing a brief description
      of the proposed action and stating the date on which (x) a record is to be
      taken
      for the purpose of such dividend, distribution or rights, or (y) such
      reclassification, reorganization, consolidation, merger, conveyance, lease,
      dissolution, liquidation or winding up is to take place and the date, if any
      is
      to be fixed, as of which the holders of Common Stock or the Preferred Stock
      or
      other securities shall receive cash or other property deliverable upon such
      reclassification, reorganization, consolidation, merger, conveyance,
      dissolution, liquidation or winding up.





(i)  RECLASSIFICATION,
      REORGANIZATION OR MERGER .
      In case
      of any reclassification, capital reorganization or other change of outstanding
      shares of Preferred Stock of the Company, or in case of any consolidation or
      merger of the Company with or into another corporation (other than a merger
      with
      a subsidiary in which merger the Company is the continuing corporation and
      which
      does not result in any reclassification, capital reorganization or other change
      of outstanding shares of Preferred Stock of the class issuable upon exercise
      of
      this Warrant) or in case of any sale, lease or conveyance to another corporation
      of the property of the Company as an entirety, the Company shall, as a condition
      precedent to such transaction, cause effective provisions to be made so that
      the
      Holder shall have the right thereafter by exercising this Warrant at any time
      prior to the expiration of the Warrant, to purchase the kind and amount of
      shares of stock and other securities and property receivable upon such
      reclassification, capital reorganization and other change, consolidation,
      merger, sale or conveyance by a holder of the number of shares of Preferred
      Stock which might have been purchased upon exercise of this Warrant immediately
      prior to such reclassification, change, consolidation, merger, sale or
      conveyance. Any such provision shall include provision for adjustments which
      shall be as nearly equivalent as may be practicable to the adjustments provided
      for in this Warrant. The foregoing provisions of this Section (i) shall
      similarly apply to successive reclassifications, capital reorganizations and
      changes of shares of Preferred Stock and to successive consolidations, mergers,
      sales or conveyances. In the event that in connection with any such capital
      reorganization or reclassification, consolidation, merger, sale or conveyance,
      additional shares of Preferred Stock shall be issued in exchange, conversion,
      substitution or payment, in whole or in part, for a security of the Company
      other than Preferred Stock, any such issue shall be treated as an issue of
      Preferred Stock covered by the provisions of Subsection (1) of Section (f)
      hereof.




5





(j)  REGISTRATION
      UNDER THE SECURITIES ACT OF 1933 .
      Until
      the expiry date of this Warrant, the provisions of the Registration Rights
      Agreement dated as of even date herewith between the Holder of the Warrants
      and
      the Company shall apply to registration of the Warrant Shares. The Company’s
      agreements with respect to Warrants or Warrant Shares in such Registration
      Rights Agreement shall continue in effect regardless of the exercise and
      surrender of this Warrant.





RESTRICTIVE
      LEGEND .
      Each
      Warrant Share, when issued, shall include a legend in substantially the
      following form: THESE SHARES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
      ACT
      OF 1933 (THE “ACT”) NOR UNDER ANY STATE SECURITIES LAW AND MAY NOT BE PLEDGED,
      SOLD, ASSIGNED OR OTHERWISE TRANSFERRED UNTIL A (1) REGISTRATION STATEMENT
      UNDER
      THE ACT AND ANY APPLICABLE STATE SECURITIES LAW HAS BECOME EFFECTIVE WITH
      RESPECT THERETO, OR (2) RECEIPT BY THE COMPANY OF AN OPINION OF COUNSEL TO
      THE
      COMPANY TO THE EFFECT THAT REGISTRATION UNDER THE ACT OR APPLICABLE STATE
      SECURITIES LAW IS NOT REQUIRED IN CONNECTION WITH THE PROPOSED
      TRANSFER.





The
      Company will not, by amendment of its charter or through reorganization,
      consolidation, merger, dissolution, sale of assets or any other voluntary
      action, avoid or seek to avoid the observance or performance of any of the
      terms
      of this Warrant, but will at all times in good faith assist in the carrying
      out
      of all such terms and in the taking of all such action as may be necessary
      or
      appropriate in order to protect the rights of the Holder of this Warrant against
      impairment.


Dated:
      June __2007





SPECTRASCIENCE,
      INC.





Attest:


By:
                Name:
            
            Name:
                Title: Secretary
            
            Title:
                Chairman and
                CEO





6




PURCHASE
      FORM




Dated
      _____________ 20__





The
      undersigned hereby irrevocably elects to exercise the within Warrant to the
      extent of purchasing ___________ shares of Preferred Stock and hereby
      makes payment of ___________ in payment of the actual exercise price
      thereof.





INSTRUCTIONS
      FOR REGISTRATION OF STOCK





Name
      ___________________________________________________________


(Please
      typewrite or print in block letters)


Address
      _________________________________________________________


Signature
      __________________________________________________





ASSIGNMENT
      FORM




FOR
      VALUE
      RECEIVED, ________________________________ hereby sells, assigns and transfers
      unto





Name
      ____________________________________________________________


(Please
      typewrite or print in block letters)





Address
      __________________________________________________________





the
      right
      to purchase Preferred Stock represented by this Warrant to the extent of _______
      shares as to which such right is exercisable and does hereby irrevocably
      constitute and appoint ________________ Attorney, to transfer the same on the
      books of the Company with full power of substitution in the
      premises.




Date
      ______________, 20__





Signature
      __________________________




7