APPENDIX 

 THE PROTEINS AND THEIR SPLIT PRODUCTS 



The nonspecific reaction, as we have seen, is elicited most fre- 

 quently by colloidal substances, either injected therapeutically or 

 originating in the tissues as a result of some inflammation (turpen- 

 tine injection, burn, trauma, etc.). Luithlen has as a result used the 

 term "Colloidal Therapy" to designate the form of treatment. Of 

 the various colloids we find the proteins and their derived products 

 most commonly used and it may be proper, therefore, to review very 

 briefly the salient facts concerning their classification, structure and 

 behavior. 



The native proteins consist of exceedingly complex molecules which 

 in turn are built up of combinations of amino acids. The final 

 molecule is a large one, does not diffuse through parchment, collodion 

 or animal membrane, frequently gives a faint opalescence in solu- 

 tion, is usually amorphous but when in pure form can be crystallized 

 under certain conditions. Chemically the proteins are relatively 

 stable and inert and are amphoteric, combining with both the hydro- 

 gen and the hydroxyl ion. They can be hydrolyzed both by acids and 

 alkalies as well as by enzymes, yielding a series of degradation 

 products commonly referred to as protein split products. These lat- 

 ter vary in character, in amount, and in composition with the protein 

 undergoing lysis, the method used in bringing about the disintegration, 

 and the time at which the material is examined. 



For convenience we may use the so-called American classification 

 of the proteins which divides them into three main classes: 



A. Simple proteins. 



B. Conjugate proteins. 



C. Derived proteins. 



The Simple (or Native) Proteins. These are naturally occur- 

 ring proteins which on hydrolysis yield only a-amino acids or their 

 derivatives. 



Albumins. Simple proteins, coagulable by heat, soluble in water 

 and dilute salt solutions. Ovalbumin, serum albumin belong to this 

 group. On injection they are followed by little or no reaction unless 

 the organism has been previously sensitized. 



Globulins. Simple proteins, heat coagulable, insoluble in water 

 but soluble in dilute solutions of salts of strong bases or acids. Serum 

 globulin is an example. 



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