250 THE INCOME OF ENERGY 



proteid in each tube and state the per cent that 

 has passed through the membrane. 



Diffusion through Living Intestinal Wall. 1 

 Through a small opening in the linea alba of a 

 fasting anaesthetized cat 2 draw out a loop near 

 the middle of the small intestine. Eemove the 

 contents by careful stroking. Tie double liga- 

 tures 0.5 cm. apart around the intestine at one 

 end of the loop and similar ligatures at a point 

 30 cm. from the first pair. With a hypodermic 



cipitate. 1 Wash with water. Redissolve in water containing 

 0.1 per cent sodium hydrate. 



Quantitative Estimation of A ITcali-albumin. Neutralize a 

 measured quantity of the solution. Separate the neutralization 

 precipitate upon a weighed filter. Wash with water, alcohol, 

 and ether. Dry and weigh. 



Preparation of Peptones. The separation of peptone from 

 the albumoses 2 with which it is obtained in the tryptic diges- 

 tion of proteids is so difficult that it should not be attempted 

 in these experiments. Add commercial peptone, often contain- 

 ing albumoses as an impurity, to a small quantity of boiling 

 neutral distilled water. Filter. 



Quantitative Estimation of Peptone. To 10 c.c. of the liquid 

 add alcohol in such proportion that the mixture shall contain 

 80 per cent. Filter through weighed filter paper. Dry at 

 40 C. Weigh. [This method is not exact, but is to be pre- 

 ferred for the purpose in hand.] 



1 VOIT and BAUER : Zeitschrift fiir Biologic, 1869, v, p. 562. 



2 These and subsequent operations will be done by an in- 

 structor assisted by a committee of the class. 



1 HAWK and GIES : American Journal of Physiology, 1902, vii, p. 460. 



2 KUHNE : Zeitschrift fur Biologie, 1892, xxix, p. 1. 



