312 VETERINARY PHYSIOLOGY 



sulphate, indicating the formation of devbtevo-proteoses ; 

 and, if the filtrate after precipitating this be tested, the 

 presence of yet another set of proteins may be demonstrated. 

 These are Peptones (p. 18) (Chemical Physiology). 



These changes may be represented in the following 

 table : — 



Coagulated Protein. 



I 

 Soluble Native Protein. 



I 

 Meta-proteins. 



I 

 Proto-proteoses. 



I 

 Deutero-proteoses. 



I 

 Peptones. 



The process is one of breaking down a complex molecule 

 into simpler molecules, probably with hydration. It is the 

 first step to the more complete disintegration of the protein 

 to amino-acids which seems necessary before it can be built 

 into the special protoplasm of the body of the particular 

 animal. 



On certain proteins and their derivatives the gastric juice 

 has a special action. On collagen the HCl acts slightly in 

 converting it to gelatin. The gastric juice acts on gelatin, 

 converting it to a gelatin peptone. 



On nucleo-proteins it acts by digesting the protein part 

 and leaving the nuclein undissolved. 



Hcenioglobin is broken down into haematin and globin, 

 and the latter is changed into peptone. It is the formation 

 of acid haematin (p. 490) which, after a short time, gives the 

 vomited matter in cases of hsemorrha^e into the stomach a 

 brown colour. 



The caseinogen calcium compound of milk (p. 636) 

 is first coagulated, and then changed to peptone. The 

 coagulation is brought about by what is generally described 

 as a second enzyme of the gastric juice — rennin. Very 

 probably this action is merely a phase of the action of pepsin. 



The stomach contains an enzyme, lipase, which splits Fats 



