72 THE CHEMISTRY OF CATTLE FEEDING 



tryptophane. For example, trypsin rapidly converts native 

 proteins into leucine, tyrosine, etc., and a remainder which 

 gives the biuret reaction (i.e. it is a peptone), when all the 

 tyrosine is removed. This remainder has been called anti- 

 peptone, and the less resistant part is called hemi-peptone. 

 The original protein, therefore, appears to be composed of two 

 groups of radicles which are known as the hemi-group and the 

 anti-group respectively. 



Classification. The original method of classifying proteins 

 according to their origin and solubility, is at once arbitrary 

 and unsatisfactory, and has been the cause of much confusion. 

 In recent years it has been modified by taking into considera- 

 tion the composition and properties of the compounds ; but 

 sufficient data are not yet available to allow of this the only 

 scientific method being made the primary basis of classifica- 

 tion. The following scheme was adopted by the Chemical and 

 Physiological Societies in 1907, but it must be regarded as 

 tentative and incomplete. 



CLASSIFICATION OF PROTEINS. 



Native proteins 



Derivatives 



Simple 



Conjugated 



Meta-proteins 



Proteoses 

 Peptones 



Polypeptides 

 Amino-acids 



Albumins. 



Globulins. 



Phospho-proteins. 



Glutelins. 



Gliadins. 



Histones. 



Protamines. 



Sclero-proteins. 



Nucleo-proteins. 



Gluco-proteins. 



Chromo-proteins. 



Acid albumins. 

 Alkali albumins. 



Albumoses, etc. 



The terminology employed in this classification is not 



