58 CHEMICAL PHYSIOLOGY. 



becoming slightly turbid. After two hours, still no change 

 is observable in B and 0. 



(c.) Filter A, and carefully neutralise the nitrate with 

 very dilute hydrochloric or acetic acid = a precipitate of 

 hemialbumose. Filter off the precipitate, and on testing the 

 nitrate, peptones are found. 



(d.) Filter B and C, and carefully neutralise the nitrates. 

 They give no precipitate. No peptones are found. 



(e.) Test the proteolytic power of an extract of Kiihne's 

 "pancreas powder" (Lesson VIII., 1, e.) 



5. Products other than Peptones. Leucin and Tyrosin (Indol). 



(a.) Place 300 cc. of a 1 per cent, solution of sodic 

 carbonate in a flask, add 5 grammes of boiled fibrin, 5 cc. 

 of glycerin extract of pancreas, and a few drops of an alcoholic 

 solution of thymol. Keep all at 38 C. on a water-bath 

 for six to ten hours. 



(b.) After six hours take a portion of the mixture, filter, 

 and to the filtrate cautiously add dilute acetic acid to preci- 

 pitate any hemialbumose that may be present in it. Filter 

 and evaporate the filtrate to a small bulk, and precipitate 

 the peptones by a considerable volume of alcohol. Filter to 

 remove the peptones, and evaporate the alcoholic filtrate to 

 a small bulk, and set it aside, whenleucin separates first, and 

 crystals of tyrosin afterwards. Keep them for microscopic 

 examination. 



(c.) A much better method of obtaining leucin and tyrosin 

 is to digest, at 40 C., for five or six hours, equal parts of 

 fresh moist fibrin and ox-pancreas with a sufficient quantity 

 of thymolised water. Boil part of the liquid, and evaporate 

 a small quantity of it, or merely place a drop on a glass 

 slide and allow it to evaporate, when beautiful microscopic 

 crystals of leucin and tyrosin are obtained. Continue the 

 digestive process of the remainder of the liquid for a few 

 hours, until the mixture emits a very disagreeable odour. 

 This fluid gives the chlorine and indol reaction splendidly. 



(d.) Examine the crystals of leucin and tyrosin microscopi- 

 cally. The former occurs as brown balls, often with radiat- 

 ing lines, not unlike fat, but much less refractive, and the 



