UTILISATION OF PROTEIDS IN THE ANIMAL 173 



maintenance of the supply of numerous other hormones. In 

 my opinion, such a call, made by special organs upon the 

 tissues generally, may necessitate a (hydrolytic) nitrogenous 

 breakdown during hunger quite as much as the maintenance 

 of the weight of the heart, nervous system, etc. ; and it would 

 go on even while a store of fat and carbohydrate is still 

 available for energy supply. I have raised this point here 

 because it seems to me to illustrate anew the interdependence 

 of all tissues, and strengthens one's belief in the physiological 

 importance of autolysis. Such phenomena, though exaggerated 

 in actual starvation, may well occur under normal conditions 

 to a less degree. Supply from the gut is not always con- 

 temporaneous with sudden needs, and a general readiness on 

 the part of the whole body to supply nutrition to any one 

 part under stress of circumstances may be secured by the 

 existence of autolytic ferments. 



If intracellular ferments function physiologically in this sort 

 of way, it becomes a question as to how their activity is con- 

 trolled. Schryver has found that acidity accelerates the course 

 of autolysis, while alkalinity diminishes its rate. He advances 

 the view that the ammonia made available during the digestion 

 of food-proteids in the gut maintains tissue alkalinity, while in 

 its absence, as during starvation, the acids produced by other 

 metabolic processes in tissue cells activise the ferments, and 

 so determine autolysis. But there is no evidence, so long as 

 oxidation is efficient, that the muscles of a starving animal are 

 more acid than those of a well-fed one, and it is difficult to see 

 how this intestinal supply of ammonia can affect the reaction of 

 other tissues than the liver, in which it is converted into urea, 

 and we know that the administration of fats and carbohydrates, 

 alone, can reduce, if it cannot prevent, tissue breakdown. 



The exact relation of autolytic ferments to metabolic pro- 

 cesses cannot be regarded as settled ; but their discovery has 

 added interest to the subject, and will continue to suggest 

 fresh lines of experimental attack. 



Much of what has been written about proteid metabolism 

 in past years has been on the lines of a controversy in which the 

 protagonists were Voit and Pfluger. It was outside the scope 

 and intention of this brief review to deal with such a historical 

 controversy ; but the fact that the high authority of Professor 

 Pfluger is still on the side of a conception which in some 



