CAUSES OF DISEASE. 25 



recovery. This curious fact is the result of natural 

 phenomena. 



Animal experiments have taught us that 

 when certain substances injurious to the 

 Antibodies, well-being of an animal are introduced 

 into the blood, other substances are formed 

 which have the power of neutralizing 

 further injections of the first. Substances manufac- 

 tured by a living organism in this way are technically 

 called "antibodies;" and the antitoxins of commerce, 

 which are prepared from living animals by inoculating 

 them with the toxins (poisons) of various diseases 

 belong to this class. Antibodies are formed in an animal 

 only when the substances which give rise to them 

 have destroyed a certain amount of tissue, the injured 

 tissues supplying the stimulants w^hich incite to activity 

 the protective functions of the body. When produced, 

 antibodies have no beneficial effects whatsoever upon 

 the tissues already destroyed, but act simply either to 

 neutralize any additional toxin which may yet be 

 circulating, or which may get into the body from the 

 exterior at another time. For these reasons antitoxins 

 are intrinsically prophylactic^ rather than curative, in as 

 much as if inoculated into a healthy person, they guard 

 against disease by preventing tissue destruction ; whereas 

 after infection, they safe-guard the body from greater 

 injury than has already occurred by neutralizing any 

 circulating poison. It is this latter action which has 



