154: ORIGIN OF NATURAL IMMUNITY, 



creatic nor the intestinal juices were by themselves bacteriolytic, 

 although together they were. 



In the intestine we have a bactericidal action, and the dead 

 cells will naturally call into being appropriate digestive enzymes; 

 and furthermore, the constituents of the bacteriol3'sed cells will, 

 together with the digested constituents of the dead micro- 

 organisms, be absorbed b}' the mucous membrane, in the cells of 

 which, or possibly in some more i-emote organ, they may, if the 

 products of digestion can stimulate the formation of digestive 

 enzymes, give rise to what are known as immune bodies. 



When an animal dies, micro-organisms swarm into the tissues 

 from the alimentary tract, and soon there is an active decomposi- 

 tion of the whole organic structure of the corpse. Why does 

 not this occur in the living animal 1 That the mucous membrane 

 of the alimentary, and especial]}^ of the intestinal, tract is 

 impervious to bacteria because the animal, and therefore the 

 epithelial lining cells are endowed with life, is rather a feeble 

 explanation, since it refers the question to the unquestionable. 

 That the living tissues are normall}^ protected admits of little 

 doubt, but how are they so ? It is known that the mother confers 

 immunity upon the offspring, that is to say, she transfers a quantity 

 of the immune bodies that she possesses. These are sufficient to 

 render the young animal immune for some time. But when these 

 are exhausted, as in time they must be, whence does it obtain its 

 own supply 1 Are we justified in saying that the immunity 

 bestowed upon the child by the mother is of a permanent and 

 creative nature, that it persists throughout the life of the child, 

 and is by it bestowed upon its descendants, generation after 

 generation, through all time ? No ! Before the maternal allot- 

 ment is exhausted the offspring must have manufactured, and be 

 capable of producing on its own account, immune bodies of its 

 own, among which are the bacteriolytic enzymes. 



When weakened pathogenic bacteria are introduced into the 

 tissues of an animal they are rapidly dissolved or digested, and 

 at the same time they stimulate the cells to secrete the diverse 

 immune bodies which confer an increased immunity upon the 



