FERMENTATION 255 



Bleed the animal from the carotid artery, re- 

 ceiving the blood into an equal volume of satu- 

 rated solution of ammonium sulphate, to prevent 

 coagulation. Eemove the intestinal loop by cut- 

 ting between the double ligatures. Measure the 

 liquid remaining in the intestine. It will be 

 found that most of the peptone has disappeared. 

 Test the blood and the urine for peptone 1 



1 Recognition of Peptone in Blood. To the blood already 

 mixed with an equal volume of ammonium sulphate solution 

 add crystals of ammonium sulphate to saturation. Filter from 

 the precipitated proteids. To the clear filtrate apply the biuret 

 test for peptone. 



Biuret reaction. To the saturated ammonium sulphate 

 filtrate add half its volume of saturated solution of potassium 

 hydrate. Shake the dense precipitate. Allow the tube to 

 stand two or three minutes until the heat developed by the 

 chemical action passes off. Add a drop of very dilute solution 

 of cupric sulphate. The fluid, dense white from the precipitated 

 salts, assumes a pale blue color, due to the solution of hydrated 

 cupric oxide in the ammonia generated. The same quantity of 

 saturated potassium hydrate as before is now allowed to flow 

 down the tube, and to form a layer at the bottom. If peptone 

 is present a rose red ring is formed at the junction of the two 

 layers. The contrast of the red ring with the pale blue above 

 it renders the test very delicate (Neumeister's method modified 

 by Shore : Journal of Physiology, 1890, xi, pp. 532-534). 



Recognition of Peptone in Urine. Remove the coloring 

 matter by (1) adding solid lead acetate and filtering from the 

 heavy precipitate ; (2) adding to the filtrate ammonium sul- 

 phate, and filtering from the copious precipitate of lead sulphate ; 

 (3) saturating the filtrate with crystals of ammonium sulphate 

 and filtering from the additional precipitate. On filtration the 



