564 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



syphilis. The antigen, however, is different. When working with specific 

 bacteria a suspension of bacterial cells in 0.85 per cent sodium chloride 

 solution constitutes the antigen. 



CYTOTOXINS AND CYTOLYSINS. The names cytotoxin and cytolysin 

 are used synonymously and are applied to those substances in sera and 

 other body fluids which have the power of destroying cells. In a broad 

 sense any substance destroying a cell would be cytotoxic but the terms 

 are usually applied in the more limited manner, as above indicated. 



Cytotoxins are produced in the same manner as other antibodies. 

 The immunization of an animal, for example, with renal cells, produces in 

 the blood serum of that animal a cytotoxin for the parenchymatous cells 

 of the kidney. Cytotoxins can be produced for practically all the paren- 

 chymatous 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 parenchymatous cells such as those of the liver. 

 In the beginning it was supposed that the cytotoxins would be of value in 

 the study of the physiological functions of organs and tissues. For 

 example, a cytotoxin having been produced for the thyroid gland or ad- 

 renal 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 impracticable. The fact that cyto- 

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

 immunization also indicates that there are similar chemical substances 

 in the various cells. 



There are autocytotoxins produced in the body and 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" would result in that 

 more of the specific cells of the organ or tissue used would be destroyed. 

 Cytotoxins have been prepared for leucocytes and these substances are 

 sometimes developed during the progress of an infection. The leucocy- 

 totoxins have perhaps been studied more than any of the rest. 



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



