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ture resembles qualitatively, though obviously not quantitatively, that noted by Greep in his male and female parabionts, both under the stimulation of one pituitary. Parabiotic studies can thus not be regarded as evidence concerning the number of gonadotrophins secreted by the pituitary. Such evidence can be obtained only from the isolation of the pure hormones from the blood as it has been done from the pituitary.Summary. A mixture of purified FSH and ICSH was shown to produce predominantly follicle-stimulating effects in female and interstitial cell-stimulating effects in male hypophysectomized rats. These differences in the response of the two sexes were secured by the simultaneous adriiinistration of both hornioiies and it would consequently not seem valid to interpret such phenomena as evidence for the existence of a single pituitary gonadotrophin.The observations here reported comprise a part of a more comprehensive study undertaken jointly by the Departments of Medicine and Pediatrics of the Johns Hopkins University on experimental amino acid deficiencies in man. The purpose of this study was twofold. It was felt desirable to determine human amino acid requirements by direct observations on man, rather than by inferences based on animal experiments, since it is now known that even closely related animal species differ in their amino acid requirements. A second purpose was to discover whether deficiencies of particular amino acids produced characteristic pathological changes which could be recognized by clinical or laboratory technics. It seemed probable that, in certain parts of the world at least, specific amino acid deficiencies might be present, and that a familiarity with the picture,

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