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  <xs:element id="biib_SolothurnSwitzerlandMember" abstract="true" name="SolothurnSwitzerlandMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
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  <xs:element id="biib_FumarateMember" abstract="true" name="FumarateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
