404 SHIGEYUKI KOMINE 



ing, the non-protein nitrogen content in the brain shows a defi- 

 nite periodic change. Under the same conditions, similar 

 periodic phenomena should occur in other organs, and it will be 

 highly interesting to test this inference on some other occasion. 

 In this connection the observations made by Pepper and Austin 

 ('15) on the content of non-protein nitrogen in the blood of 

 dogs are very valuable. Pepper and Austin found that by 

 feeding a dog with a moderate amount of meat, the blood nitro- 

 gen reaches a maximum within about two hours after feeding, 

 and returns to the original level in about ten to fourteen hours. 



When, however, the dog was allowed to fast, the blood nitro- 

 gen first falls gradually below the original level until it reaches a 

 minimum at thirty to forty-eight hours, and then begins to rise 

 gradually during a few hours, after which it tends to persist. 



From the functions of the blood we can at once appreciate 

 the relations of the observations of Pepper and Austin to the 

 present study, because the blood receives the digestive products 

 and distributes these to the tissues and organs. 



When autolysis begins in the tissues and organs as the result 

 of fasting, these autolytic products are again poured into the 

 circulation. Consequently, what Pepper and Austin observed 

 in the blood reveals what is probably happening in the organs and 

 tissues. In reality the content of non-protein nitrogen in the 

 blood indicates the periodic changes following first feeding and 

 then fasting, as w^as observed by me in the brain of rats. Owing 

 to the differences in the body size, as well as to the different 

 degrees of activity of these two animals, the exact time relations 

 found by Pepper and Austin cannot be directly compared with 

 what has been found in the rat brain. 



Very recently'' Mitchell ('18) studied the partition of non- 

 protein nitrogen in the entire body, as well as in some organs of 

 the albino rat at birth, before and after feeding. Mitchell 

 noted in the younger rats a decided increase of non-protein 

 nitrogen soon after feeding when compared with that in the 

 rats fasting for twenty-four to forty-eight hours. In the case of 

 adult rats, however, this increase was not as conspicuous as in 

 the younger rats. The observed period following feeding was 



