326 DIGESTION OF PROTEIDS. [BOOK n. 



since in that case a violet colour, deepening on boiling, that is 

 the ordinary proteid reaction, is obtained. There are reasons for 

 thinking that there are several kinds or at least more than one 

 kind of peptone ; but we may for the present speak of the sub- 

 stance as one. 



Albuniose differs from peptone, not only in being precipitated 

 by ammonium sulphate but also in being much less diffusible, 

 and in other minor characters. Albumose like peptone gives the 

 biuret reaction. We are able to distinguish several kinds of 

 albumose, but into the details of these we need not enter. The 

 amount of albumose appearing in a digestion experiment, rela- 

 tive to the amount of true peptone, depends on the activity of 

 the juice, and other circumstances. We may regard albumose 

 as a less complete product of digestion than peptone. For a long 

 time albumose was confounded with peptone, and many of the 

 commercial forms of "peptone" consist largely of albumose. 



When fibrin, either raw or boiled, or any form of coagulated 

 proteid is dissolved and seems to disappear under the influence 

 of gastric juice, the same products, albumose and peptone, make 

 their appearance. The same bodies result when myosin or any 

 one of the globulins or acid-albumin or alkali-albumin is subjected 

 to the action of the juice. 



Besides albumose other bodies, which may also be regarded as 

 less complete products of digestion, make their appearance, to a 

 variable extent under different circumstances when proteid is 

 digested with gastric juice. On these bodies however, known as 

 parapeptone and by other names, we need not dwell. 



It is obvious that the effect of the action of the gastric juice 

 is to change the less soluble proteid into a more soluble form, the 

 change being either completed up to the stage of peptone, the 

 most soluble of all proteids, or being left in part incomplete. 

 This will be seen from the following tabular arrangement of 

 proteids according to their solubilities. 



Soluble in distilled water. 



Aqueous solutions not coagulated on boiling. 



Diffusible Peptone. 



Much less diffusible Albumose. 



Aqueous solutions coagulated on boiling . Albumin. 



Insoluble in distilled water. 



Eeadily soluble in dilute saline solutions 



(NaCl 1 per cent.) Globulins. 



Soluble only in stronger saline solutions 



(NaCl 5 to 10 p. c.) Myosin. 



