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  <xs:element id="si_SeriesDWarrantsMember" abstract="true" name="SeriesDWarrantsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="si_ReportableSegmentMember" abstract="true" name="ReportableSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="si_MedicalEducationExpense" abstract="false" name="MedicalEducationExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="si_StifelLoanAgreementMember" abstract="true" name="StifelLoanAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="si_TrinityLoanAgreementMember" abstract="true" name="TrinityLoanAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="si_TermLoanMember" abstract="true" name="TermLoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="si_LineofCreditFacilityAccordionFeatureIncreaseLimit" abstract="false" name="LineofCreditFacilityAccordionFeatureIncreaseLimit" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="si_DebtInstrumentPrepaymentPremiumPercentOfPrincipalOutstanding" abstract="false" name="DebtInstrumentPrepaymentPremiumPercentOfPrincipalOutstanding" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="si_DebtInstrumentPrepaymentPremiumAndEndOfTermPayment" abstract="false" name="DebtInstrumentPrepaymentPremiumAndEndOfTermPayment" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="si_RobertBallMember" abstract="true" name="RobertBallMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
