INTRODUCTION 19 



demonstration that bacteria are not only proteins, but 

 relatively complex proteins, is a matter of marked impor- 

 tance. It shows that in many of their life processes they 

 must bear a close resemblance to the cells of the higher 

 animals; that they require the same kind of food, which 

 they select, assimilate, and excrete in much the same way; 

 that the conditions of life are much the same; what is favor- 

 able to one bearing a like relation to the other, and what 

 proves injurious to one having a like effect upon the other. 

 2. All true proteins contain a poisonous group. At first 

 we found that the cellular substance of certain pathogenic 

 bacteria could be split up with the liberation of a poisonous 

 substance, then we tested non-pathogenic bacteria, then 

 animal and vegetable proteins, and all with the same result. 

 Not only do all these contain a poison, but so far as its 

 gross effects on the higher animals have been studied, the 

 same poison. We have held that when we know more 

 about these poisonous bodies obtained from all proteins, 

 it will be found that chemically they are not identical, but 

 physiologically they are so closely similar that up to the 

 present time we have not been able to distinguish one 

 from the other by the symptoms induced. The poison 

 obtained from the typhoid bacillus, that from egg-white, 

 and that from edestin of hemp-seed kill animals in the same 

 doses, with the same symptoms and with the same lesions. 

 This is striking evidence of the similarity in the structure 

 of the protein molecule, whether it be of bacterial, animal, 

 or vegetable origin. One cannot resist the temptation to 

 formulate a theory to fit these facts. Indeed, the theory 

 unfolds itself and may be briefly expressed as follows: All 

 proteins are constructed on the same model and contain a 

 chemical nucleus, archon, or key-stone. This is the poison- 

 ous group and is practically the same in all proteins. One 

 protein differs from all others in its secondary and possibly 

 its tertiary groups. In these lies the specificity of proteins. 

 Living proteins function through their secondary and 

 tertiary groups. When the primary group is detached 

 from its own subsidiary and specific groups it manifests 



