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  <xs:element id="msif_InvestmentCompanyTaxBasisNetIncomeLossAttributableToParentEstimated" abstract="false" name="InvestmentCompanyTaxBasisNetIncomeLossAttributableToParentEstimated" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
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  <xs:element id="msif_InvestmentCompanyTaxBasisTaxableIncomeEarnedPriorToPeriodEndAndCarriedForwardForDistributionNextPeriod" abstract="false" name="InvestmentCompanyTaxBasisTaxableIncomeEarnedPriorToPeriodEndAndCarriedForwardForDistributionNextPeriod" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
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  <xs:element id="msif_InvestmentCompanyTaxBasisDistributionsAccruedOrPaidToCommonStockholders" abstract="false" name="InvestmentCompanyTaxBasisDistributionsAccruedOrPaidToCommonStockholders" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
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  <xs:element id="msif_InvestmentIncomeOperatingDeferredFederalTaxExpenseBenefit" abstract="false" name="InvestmentIncomeOperatingDeferredFederalTaxExpenseBenefit" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="msif_InvestmentIncomeOperatingDeferredStateAndOtherTaxExpenseBenefit" abstract="false" name="InvestmentIncomeOperatingDeferredStateAndOtherTaxExpenseBenefit" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
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  <xs:element id="msif_InvestmentTaxExpenseIncomeDeferredAbstract" abstract="true" name="InvestmentTaxExpenseIncomeDeferredAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
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  <xs:element id="msif_RealizedGainLossInvestmentAndDerivativeOperatingDeferredTaxExpenseBenefit" abstract="false" name="RealizedGainLossInvestmentAndDerivativeOperatingDeferredTaxExpenseBenefit" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
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  <xs:element id="msif_InvestmentCompanyNumberOfAdditionalInvestmentsCommitmentsRestrictedForFundExpensesOrFollowOnInvestmentsInExistingPortfolio" abstract="false" name="InvestmentCompanyNumberOfAdditionalInvestmentsCommitmentsRestrictedForFundExpensesOrFollowOnInvestmentsInExistingPortfolio" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="msif_MSCIncomeMember" abstract="true" name="MSCIncomeMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="msif_AdvisoryAgreementMember" abstract="true" name="AdvisoryAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
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  <xs:element id="msif_AdvisoryAgreementIncentiveRateQuarterlyHurdleRateMember" abstract="true" name="AdvisoryAgreementIncentiveRateQuarterlyHurdleRateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="msif_AdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember" abstract="true" name="AdvisoryAgreementIncentiveRateAnnualizedHurdleRateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="msif_AdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember" abstract="true" name="AdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeBelowCatchUpThresholdMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="msif_AdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember" abstract="true" name="AdvisoryAgreementIncentiveRateQuarterlyCatchUpThresholdMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="msif_AdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember" abstract="true" name="AdvisoryAgreementIncentiveRateAnnualizedCatchUpThresholdMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="msif_AdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeExceedsCatchUpThresholdMember" abstract="true" name="AdvisoryAgreementIncentiveRatePreIncentiveFeeNetInvestmentIncomeExceedsCatchUpThresholdMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
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  <xs:element id="msif_AnnualInterestRateDomain" abstract="true" name="AnnualInterestRateDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
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  <xs:element id="msif_AnnualInterestRateGreaterThanBillionMember" abstract="true" name="AnnualInterestRateGreaterThanBillionMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="msif_AdviserAgreementAnnualBasisPointReimbursementPercent" abstract="false" name="AdviserAgreementAnnualBasisPointReimbursementPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
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  <xs:element id="msif_InterestFeesAndDividendIncomeSecuritiesOperating" abstract="false" name="InterestFeesAndDividendIncomeSecuritiesOperating" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
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</xs:schema>
