i EXCHANGE OF MATEEIAL 29 



the alimentary canal for meat ; the minimum by the quantity of 

 llesh and fat of the animal, i.e. by the state of nutrition of the 

 animal before beginning the purely meat diet. 



In the case of the dog weighing 33 kgrms., Voit obtained the 

 maximum limit for the nitrogenous equilibrium with 2500 grms. 

 of meat per day; with 2600 grins, there was a gain in the 

 balance; with 2900 grms. there was a deficit, caused by indiges- 

 tion, diarrhoea, sickness, discharge of undigested meat in the faeces. 

 In the same dog Voit found 480 grms. of meat insufficient for 

 the attainment of nitrogenous equilibrium. Only after a fast of 

 eleven days was this quantity of meat sufficient to give equilibrium 

 between the intake and output. Thus the limits of equilibrium in 

 the said dog extended from 2500 to 480 grms. of meat per day, 

 that is, from 85 to 16 grins, of nitrogen. 



The state of nitrogenous equilibrium, although unstable and 

 subject to slight variations, may continue for a considerable time 

 on a medium diet of meat, provided there are no disturbances of 

 metabolism due to external or internal causes, such as marked 

 variations in the surrounding temperature, muscular and nervous 

 activity differing very much in degree on the successive days of the 

 experiment. When, on the other hand, the quantity of animal food 

 reaches or approaches the maximum or minimum limit, the nitro- 

 genous equilibrium is easily disturbed, and the animal cannot live 

 for any length of time. 



Munk and Eosenheim fed a dog on a meagre quantity of meat, 

 which was, however, sufficient for nitrogenous equilibrium, and 

 found that during the sixth to the eighth week grave disturbances 

 took place, which caused the death of the animal in the course of 

 a few weeks. Jagerroos was, however, able to keep a dog alive 

 much longer under similar conditions, by giving it fresh, raw 

 meat. It is therefore possible that in Munk's experiment illness 

 and death were not brought about by a too scanty diet and conse- 

 quent exhaustion from a slow process of inanition, but by other 

 causes connected with the quality of the food or other disturbing 

 extrinsic or intrinsic conditions. 



If we determine, in addition to the nitrogenous exchange, the 

 intake and output of carbon, we can also find out whether fat is 

 consumed or stored in the body on a purely meat diet. According 

 as the output of carbon is in excess of or less than the intake, we 

 may conclude that fat is consumed or formed. 



The experiments made by Pettenkofer and Voit proved that if 

 only a small quantity of meat be given, the animal loses both 

 flesh and fat ; if the quantity given be increased, the loss of both 

 flesh and fat will diminish, and there will be tendency towards 

 equilibrium in both ; if the amount of meat given be again 

 increased, the consumption will increase until nitrogenous equili- 

 brium is reached, whilst carbon is retained for the formation 



