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The nucleoproteins, as their name implies, are the proteins of cell nuclei and give to the latter their character. The nucleoproteins are therefore found in largest quantity wherever cellular material is abundant, as in glandular tissues and organs. By artificial hydrolysis or during treatment in the alimentary tract a nucleoprotein is decomposed into protein and nucleic acid. Nucleic acid, of which there are several types, may be made to yield a series of well-defined compounds, the purine bases (xanthine, hypoxanthine, adenine and guanine), the pyrimidine bases (uracile, cytosine and thymine), a carbohydrate group (pentose or hexose) and phosphoric acid. Glucoproteins are compounds of the protein molecule with a substance or substances containing a carbohydrate group other than a nucleic acid. Particularly rich in glucoproteins are the mucus-yielding portions of tissues. They serve also as a cement substance in holding together the fibers in tendons and ligaments. An amino-sugar, glucosamine, has been isolated from some of the glucoproteins and it is generally regarded as constituting the carbohydrate radicle of these conjugated proteins. Phosphoproteins are compounds of the protein molecule with some, as yet undefined, phosphoruscontaining, group other than a nucleic acid or lecithin. 8 THE AMINO ACIDS Conspicuous foods containing phosphoproteins are milk with its caseinogen and tgg yolk with its vitellin. A trace of iron is also evident in these proteins and although it is possibly present as an impurity there is no evidence that it does not exist in combination with the protein. Hemoglobins are compounds of the protein molecule with hematin or some similar substance. The coloring matter of the blood is hemoglobin which acts as oxygen carrier for the tissues and is characterized by holding iron as a constituent part in organic combination. Globin is the protein portion of hemoglobin. In certain of the lower animal forms copper enters into combination with protein forming hsemocyanin imparting a blue color to the blood. Lecithoproteins are compounds of the protein molecule with lecithins. Lecithins are complexes characterized by yielding glycerol, phosphoric acid, fatty acid radicles, and a nitrogenous base, choline. The lecithins are present in all plant and animal cells but are especially abundant in the nervous tissues. They belong to the group of essential cell constituents. C. Derived Proteins Certain of the native soluble proteins upon continued contact with water, or the influence of enzymes or acid change their character and become insoluble. Such insoluble substances are called proteans. After repeated reprecipitation globulins may become insolu-THE PROTEINS 9 ble, that is, they are changed to proteans, and it is believed by some protein investigators that nearly every protein may assume a protean state. The metaproteins may be formed from simple protein by the action of acids and alkalies. In this instance, however, the change is undoubtedly more profound than in the case of the proteans. Formerly, m...

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Salts of tartaric acid administered subcutaneously to fasting phlorhizinized animals exert a markedly detrimental influence upon the secretory efficiency of the kidney, which is indicated by a greatly lessened output of certain typical urinary constituents. A histological study of the nephritic kidney demonstrates that the salts act specifically upon the epithelium of the convoluted tubules, and to a less extent upon the tubules of the loops of Henle, the glomerules, and interstitial tissue remaining unharmed. In the disintegrative process taking place, vacuolation first occurs, is rapidly followed by necrosis, and finally the dead cells or their debris may entirely fill the lumina of the tubules and form granular and hyaline casts. There is no strict relation between the dose of tartrate and the extent of damage inflicted. While large doses invariably induce a well marked response small doses may at times produce effects equally significant. Tartrates introduced into fasting animals call forth symptoms practically identical with those observed in fasting phlorhinized animals. It is therefore apparent that in the establishment of the pathological condition under discussion phlorhizin is without significant influence. Neither the liver nor the adrenal exhibits any detrimental effect from the injection of tartrates. The introduction of tartrates by way of the mouth to fasting rabbits is not nearly so effective in the production of nephritic symptoms as the administration of much smaller doses subcutaneously. In general, under the former circumstances the initial stages only of epithelial disintegration of the convoluted tubules obtain, which, however, are scarcely sufficient to account for the rapidity with which death usually ensues. Although in well fed animals distinct pathological changes in the kidney are induced by the introduction of tartrates per os, these abnormalities are less in degree, but similar in kind, than those provoked under like conditions in the fasting animal. When tartrates are given subcutaneously to well fed rabbits the effects evoked are somewhat less pronounced than when the salts are injected into fasting animals. From these facts it is evident that the state of nutrition plays a part in the development of tartrate nephritis. It is indicated that the introduction of a sufficiency of alkali to animals in a state of fasting permits a greater elimination of urinary constituents during tartrate nephritis than obtains under similar circumstances when the alkali is omitted. Histologically there is evidence that the administration of alkali exerts a slight modifying action.