For the purpose of facilitating the economical and efficient conduct of operations in the National Institutes of Health which are financed by two or more appropriations where the costs of operation are not readily susceptible of distribution as charges to such appropriations, there is established the National Institutes of Health Management Fund. Such amounts as the Director of the National Institutes of Health may determine to represent a reasonable distribution of estimated costs among the various appropriations involved may be advanced each year to this fund and shall be available for expenditure for such costs under such regulations as may be prescribed by said Director, including the operation of facilities for the sale of meals to employees and others at rates to be determined by said Director to be sufficient to cover the reasonable value of the meals served and the proceeds thereof shall be deposited to the credit of this fund: Provided, That funds advanced to this fund shall be available only in the fiscal year in which they are advanced: Provided further, That final adjustments of advances in accordance with actual costs shall be effected wherever practicable with the appropriations from which such funds are advanced.