THE PROTEIXS AND TIIEIE METABOLISM 



115 



Tryptoplian does not give rise to glucose nor to acetone bodies. It is 

 ,,ne of the indispensable ainino acids (see page 125). It may be con- 

 sidered the mother substance of thyroxin, the principal substance of the 

 liornmne of the thyroid gland (Kendal, 1019 (c)~). 



II 

 H/\ 



-CIL-CHXIL-COOIl 



III 



ni/\. 



-CIL-CIL.-COOII 



IH\/\/0 

 f[ XII H XII 



Trvptophau Tliyroxin 



The fate of the amino acids in the body may be summarized in tbe 



following table : 



TABLE III 



FATE OF AMINO ACIDS ix THE ANIMAL BODY 



Ten of the amino-acids are known definitely to give rise to glucose, and it 

 is very possible that the four marked with the query may also give rise to 

 ulucose. 



It was found by Lusk that dogs rendered diabetic by means of phlo- 

 riiixin excrete 3.0 grams of glucose for every 0.25 grams of protein that 

 they catabolize. Lusk and Mandel showed that severe human diabetics 

 :nay excrete sugar in the same proportion, which means that from every 

 >no hundred grams of proteins catabolized. fifty-nine grams of sugar 

 'an be formed. 



This does not yet complete the tale for three of tbe amino-acids give 

 "ise to not inconsiderable quantities of acetone bodies. Glucose and 

 i^-hydroxybutyric acid seem therefore to be tbe two important stations along 



