710 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



The immunization of an animal, for example, with renal (kidney) cells, 

 produces in the blood serum of that animal a cytotoxin for the paren- 

 chymatous cells of the kidney. Cytotoxins can be produced for prac- 

 tically all the parenchymatous cells of the body. These immune bodies 

 are not very specific and even careful experimentation leads to confusing 

 results. For example, when an animal is immunized to kidney cells 

 there is produced in the body of the immune animal cytotoxins for 

 kidney cells and also cytotoxins in smaller amounts for other paren- 

 chymatous cells such as those of the liver. In the beginning it was sup- 

 posed that the cytotoxins would be of value in the study of the physio- 

 logical functions of organs and tissues. For example, a cytotoxin 

 having been produced for the thyroid gland or adrenal gland it would be 

 possible to inject this into another animal, destroy the gland, and then 

 note the effect on the body. It was thought it might be possible to 

 produce anticytotoxins which would be able to counteract the action of 

 those cytotoxic substances which are produced in the body during the 

 course of infections. However, the lack of specificity of the cytotoxin 

 renders these procedures only theoretically possible. The fact that 

 cytotoxins are produced for cells other than those used in the process of 

 immunization indicates that there are similar chemical substances in the 

 various cells. 



There are autocytotoxins produced in the body. These probably 

 result from the absorption of the products of disintegrated tissue cells. 

 If no anticytotoxins for these autocytotoxins are produced, or they are 

 not destroyed in some way, a very "vicious cycle' 3 would result in 

 that more of the specific cells of the organ or tissue used would be de- 

 stroyed. Cytotoxins have been prepared for leucocytes and these 

 substances are sometimes developed during the progress of an in- 

 fection. The leucocytotoxins have perhaps been studied more than 

 any one of others. 



When ova are used for the purpose of producing cytotoxins, besides 

 producing these substances in the serum of the immune animal, 

 cytotoxins for spermatozoa of the same species are also produced, 

 showing that these cells have some chemical substances in common. 



Metchnikoff, following his idea that old age is due to a destruction 

 of tissue by the mononuclear leucocytes, hoped that it would be possible 

 to produce a cytotoxin for these cells. It is claimed by some that there 

 are specific substances produced by the exhaustion of certain cells, 



