254 PROTEIN THERAPY 



The phosphoproteins are of interest because casein the isolated 

 protein of milk belongs in this category. This protein has been used 

 to a great extent for the nonspecific reaction. Casein itself is followed 

 by little or no general reaction when injected for the first time. It 

 has been suggested that the more marked reaction obtained with milk 

 injections is due to the bacterial content, rather than due to the 

 protein of the milk itself. Casein is practically the only one of the 

 native proteins which is subject to the action of erepsin, both of the 

 enzyme of the intestinal tract and the erepsin-like enzyme occurring 

 in the serum. 



The nucleoproteins occur not only in the proteins obtained from 

 nuclei of cells, but are present in large amounts in the material ob- 

 tained from bacterial sources in which the nucleoprotein occurs 

 throughout the cell body. The relation of these substances to the so- 

 called endotoxins of bacteria is still uncertain, v. Groer isolated 

 a nucleohiston from typhoid bacilli which he used for nonspecific 

 injections. 



The Derived Proteins. This group is an artificial one and in- 

 cludes all the decomposition products occurring after the action of 

 chemical, physical or biological agents (enzymes) on the naturally 

 occurring proteins. 



In the first group are included the proteins, metaproteins and 

 coagulated proteins, that is, proteins which have undergone the first 

 alterations following the action of heat, acids, etc. This group has 

 no importance from the therapeutic standpoint. 



In the second group are included those protein derivatives com- 

 monly called protein split products, which in turn are classified under 

 three groups Proteoses, Peptones and Peptids. 



THE PROTEOSES (ALBUMOSES). These represent the first dissocia- 

 tion products of the albumins. They are no longer heat coagulable 

 but can be salted out by concentrations of certain salts such as am- 

 monium sulphate, zinc sulphate, etc. They are by no means clearly 

 defined chemical entities, the usual preparations obtained by precipi- 

 tation including mixtures of molecules and molecular aggregates vary- 

 ing to some extent in size. The albumoses are roughly divided into 

 two groups, primary and secondary albumoses. Of these the primary 

 proteases more closely approximate the proteins from which they are 

 derived; they are precipitated by half saturation with ammonium 

 sulphate. 



The Primary Proteoses can in a general way be divided into two 

 groups by means of dialysis, whereby the hetero-albumose becomes 

 insoluble, or by the addition of an equal amount of alcohol. Hof- 

 meister's table may be of some value in illustrating the differences 

 in behavior of these higher split products of proteins. 



In general it may be stated that the primary proteoses are more 

 toxic than the secondary proteoses, but variations occur, depending 



