LECT. V. AZOTISED SUBSTANCES. 103 



a very weak solution of hydrochloric acid : the solution 

 never acquired a solvent property; it became gastric juice 

 only by contact with the membrane of the stomach. 



The property with which pepsine is endowed, requires 

 the constant presence of a free mineral organic acid. If, 

 on the other hand, pepsine be dissolved in an alkaline 

 liquid, its catalytic action becomes modified, as we shall 

 hereafter find. 



Lastly, I may remark, that pepsine loses its properties 

 and becomes insoluble, when heated beyond 50 centig. 

 [= 122 Fahr.] 



Azotised neutral substances, dissolved in the stomach by 

 the acid liquid, or by the catalytic action of pepsine, pass 

 into the blood merely by the imbibition of the coats of the 

 capillary blood-vessels of the stomach. Water, and 

 coloured alcoholic drinks, introduced into the stomach, are 

 also absorbed ; they do not pass beyond this viscus, nor are 

 they to be found in the chyle ; yet they reach the blood. 

 Bouchardat and Sandras fed animals with fibrine, coloured 

 with either saffron or cochineal, and yet could never detect 

 a trace of the colouring matter in the chyle.* Moreover, 

 animals fed on fibrine, and others which were kept fasting, 

 yielded, when killed, chyle always of the same kind: the 

 contents of the intestines in no way differed, except, that 

 in the animals fed on fibrine, a portion of the latter was 

 found in the stomach incompletely dissolved. We know, 

 also, from the celebrated experiments of Tiedman and 

 Gmelin, that the quantity of fibrine contained in the lymph 

 and chyle, after a long fast, is not less than that which is 

 found there after digestion. The results are the same when 

 coagulated albumen, gluten, and caseous matter, is em- 

 ployed instead of fibrine. The digestion of these azotised 

 neutral substances is, therefore, a mere solution, effected by 

 an action of contact, and an absorption of this solution 



