344 CARNEGIE INSTITUTION OF WASHINGTON. 



attributed to "diets containing 27 and 36 per cent of protein derived chiefly 

 from beef." For this reason it seemed desirable to have some of the tissues of 

 rats growing on our diets very high in protein subjected to histological exami- 

 nation. This has been secured through the cooperation of Professor E. A. 

 Park and his collaborators at the Yale University School of Medicine in a 

 preliminary study of some of the animals grown on the high-protein diets. 

 The only striking change was found in the kidneys, which were greatly hyper- 

 trophied, the average weight being almost twice that of the control animals 

 and their size about one-third greater. Microscopic examination showed no 

 changes of an inflammatory or degenerative nature. The exact histological 

 condition of the kidneys and of the other organs will be reported subsequently. 

 Hypertrophy of the kidneys existed without hypertrophy of the heart. The 

 ratio of the weight of the heart as well as of the liver to the body-weight was 

 about the same in the animals fed the high-protein diets as in the control 

 animals. The ratio of the weight of the kidneys to the body-weight in the 

 animals on the high-protein diets was, on the average, almost double that of 

 the control animals. The hypertrophy occurred whether the protein used was 

 of animal or vegetable origin or was rich or poor in phosphorus. 



The animals on such diets were poorly or, at best, only moderately well 

 nourished. The subcutaneous fat was scant and the skin adherent. There 

 was some fat in the abdominal cavity and in certain animals it was fairly 

 plentiful, but in none was it so abundant as in the control animals. In some 

 animals the lungs showed the infection so commonly seen in the domestic rat. 

 The thymus was invariably atrophied. The heart was normal. The spleen 

 varied greatly in size. In some rats it was large, in others normal, and in 

 others atrophic. The liver presented no gross abnormalities. The testes in 

 some of the animals were normal in size; in others they were exceedingly 

 atrophic. 



The cause of the renal hypertrophy just described is of physiological interest. 

 Is it a functional hypertrophy due to the necessity of excreting unusually large 

 quantities of the products of protein breakdown? Some of the questions here 

 involved are being considered by inducing "overwork" on the part of the kid- 

 neys through the necessitj'^ of excreting large quantities of other produ cts than 

 the nitrogenous catabolites. The effects of eliminating large quantities of 

 phosphate belong in this category. 



Through the continued cooperation of Dr. A. M. Yudkin the pathology of the 

 ophthalmia which we described long ago, and which occurs as the result of 

 deficiency of the vitamine A in the diet, has been continued. His efforts are 

 being directed to a more detailed study of the incipient stages of the patho- 

 logical changes and likewise to the extent and character of the recovery when 

 sources of the vitamine are given to the affected animals. In this connection 

 we have incidentally observed, in harmony with the reports of others, that 

 cod-liver oil through which oxygen has been bubbled for a considerable 

 time, while the fat was kept warm, loses its vitamine A potency judged by the 

 capacity to cure the ophthalmia. Mere heating of vitamine-A-bearing 

 products does not necessarily destroy the potency, for we have lately found 

 alfalfa dried in a current of air to retain its curative property. 



We have collaborated with Professor Park and his associates at the Yale 

 School of Medicine in investigations of the histological changes taking place 

 in the skeleton and other structures under conditions of diet in which one or 



