306 INFECTION AND IMMUNITY 



Other minor poisons may in some instances be demonstrated in 

 culture media, and also may possibly be formed in the animal body by 

 the metabolic activities of the germs. These are either simply waste 

 products of metabolism or bodies due to the decomposition' of the 

 nutrient media in which the germs are gowing. These bodies are usually 

 referred to as ptomains, and differ entirely from the true secreted toxins, 

 both in their chemical composition and in their physiologic action, re- 

 sembling in both of these the alkaloids. They are not known to give 

 rise to antibodies of any kind in animals. 



Apart from all the poisons just mentioned; i.e., the toxins, hemoly- 

 sins, leucocidins, and ptomains, there is supposed to exist a most vitally 

 important and interesting group of poisonous substances, the so-called 

 endotoxins. These, so far as our knowledge goes, are poisons rather 

 firmly seated in the bacterial cell, which are not secreted in our ordinary 

 cultur?2 media, and are supposed by most observers not to be separable 

 in the animal fluids and tissues from the intact bacterial cell. These 

 poisons may be demonstrated in old cultures, in which the bacteria 

 are dead and disintegrating or undergoing autolysis although Pfeiffer 

 does not consider autolytic products necessarily similar to endotoxins 

 or they may be obtained by destroying the bacteria mechanically by 

 pressure and grinding, or by breaking them while frozen. In the animal 

 body they are said to become free when the bacteria die and decompose 

 or are disintegrated by the digestive bodies by which they have been 

 attacked. These endotoxins are recognized by the fact that they 

 do not call out true antitoxins which become free in the plasma and 

 serum, but do, nevertheless, lead to the formation of digestive antibodies, 

 these not following, however, the "law of multiples" in protecting in- 

 fected animals from the poisons. The liberation of these poisons by the 

 destruction of bacteria in the animal body is best illustrated by the so- 

 called phenomenon of Pfeiffer which takes place when cholera vibrios 

 and immune cholera serum are introduced into the peritoneal cavity 

 of a guinea-pig. If specimens are withdrawn from time to time from 

 the peritoneal cavity of an animal so treated, a rapid swelling up, 

 disintegration, and disappearance of the vibrios can readily be demon- 

 strated. The organisms apparently do not multiply in the animal body 

 under these conditions and are almost immediately destroyed. This 

 disintegrating power is also claimed for the body fluids of normal 

 animals and is supposed to be demonstrated by the following experi- 

 ment. When graded quantities of a fresh cholera culture are introduced 

 into the peritoneal cavity of normal guinea-pigs of equal weight, the 



