THE BLOOD. 213 



of 1 to 500, with incubation; second, by a great dilution of the blood 

 tested, the test-serum being used pure and the test made at room 

 temperature. 



IMMUNITY. 



Normal sera may contain: 



1. Antiferments (blood-serum prevents the ferments from act- 

 ing as trypsin on proteids or a mixture of pancreatic juice and 

 enterokinase, because the kinase is neutralized). 



2. Antitoxins. 



3. Cytotoxins (cell-destroyers include hsemolysins. These hodies 

 are composed of complement and an immune "body or amboceptor). 



4. Agglutinins. 



5. Precipitins. 



ZYMOIDS.i 



There are a certain number of substances contained in the cul- 

 tures of microbes which may be in the liquids of the organism, and 

 notably in the blood-serum of normal animals and in animals vacci- 

 nated against certain microbes or their filtered cultures, which have, 

 with the ferments, a certain number of common properties. Such bodies 

 are the microbian toxins, the venoms of serpents, the antitoxins, the 

 agglutinins, the precipitins, the bacteriolysins, the haemolysins, etc. 

 Because of certain analogies to enzymes, they have been called 

 enzymoids. Toxins are the -nonalkaloidal poisons produced by 

 microbes or secreted by the animal or vegetable cell. These toxins 

 are divided into two kinds: (1) the toxalbumins, cellular secretions 

 destroyed by heat at 70 C., but not coagulating; they do not act 

 except after a period of incubation, always long, as the toxins of 

 diphtheria, of tetanus, etc. ; (2) the toxproteins, derived from cells 

 coagulating by heat, acting upon the organism, and acting without 

 a period of incubation ; these are the venoms, the proteins of plague 

 and cholera. We have also vegetable toxalbumins, as abrin from 

 jequirity, ricin from castor-oil seeds, rubin from the extract of the 

 bark of the acacias. These bodies are zymoids. The toxalbumins 

 always have a period of incubation. The phenomena shown are all 

 physiological phenomena; an infinitely small quantity of toxalbumin 

 is able to cause phenomena infinitely great. We should remember 

 that certain microbian products, as tuberculin or mullein, resist the 

 prolonged action of 100 C. without alteration. 



1 In the preparation of this article I have drawn on Arthus, "Chernie 

 Physiologique," 



