158 MICROBES AND TOXINS 



by reason. If progress went on logical lines the idea of anti- 

 bodies in general ought to have been the first, and from it the 

 existence of antitoxins ought to have been deduced. But, on 

 the contrary, it was the discovery of a particular antitoxin which 

 led to the study of antibodies in general. 



In experimental medicine, the chief business is not to build 

 up systems of ideas, i.e. t to philosophize, but simply to search 

 patiently with many trials and many a re-beginning. The 

 inquisitive, prying, intuitive people have the advantage over 

 those who reason. 



At the very beginning of the researches on toxins we find an 

 experiment of Pasteur : the filtrate of a culture of fowl cholera 

 produced in a fowl the symptoms of the disease in the absence 

 of microbes. At first it was thought that the bacterial toxins 

 belonged to the group of alkaloid substances, the ptomaines, 

 found by Selmi in dead bodies, in certain molluscs, and in 

 bacterial cultures (e.g., muscarine, neurine, &c.). It is true that 

 bacteria can produce poisons of this type (Brieger), but these 

 poisons do not produce a specific intoxication like that 

 observed in such a well-defined disease as tetanus. Later, when 

 it had been observed that microbes killed by heat are not 

 harmless, but when inoculated produce a local suppuration, 

 attempts were made to isolate the " poison " by making protein 

 extracts of the bacterial bodies ; but the bacterial proteins 

 of H. Buchner are not specific poisons ; from very diverse 

 bacteria one can extract almost the same poisons. They con- 

 sist of excretions or residues of nutrition of the bacteria, and 

 are found in particular in old cultures. 



Excluding these alkaloids and proteins, the following are the 

 substances studied as toxins : 



1. The Soluble Toxins. The type-specimen is the diphtheria 

 toxin or the tetanus toxin. These are secretions of bacterial 

 cells, just as the pancreatic juice is a secretion of the gland 

 cells. 



2. The Endotoxins. Examples : typhoid endotoxin, plague 

 endotoxin. These are poisons which remain attached to the 

 cellular protoplasm, and do not diffuse at all or very little in 



