THE THEORY OF TOXIC ACTION 205 



We thus cannot say what the mechanism is by which these 

 poisons act. It may be said that Macfadyen, by grinding up 

 typhoid bacilli frozen by liquid air, claimed that on thawing he 

 obtained the intracellular toxins in liquid form, and he further 

 stated that by using this fluid he could immunise animals not 

 only against the toxins but also against the living bacteria. 



We have already pointed out that those who claim for the 

 aggressins a special character hold that the activity of these 

 bodies has as its effect the interference with the phagocytic 

 functions of the leucocytes. They also hold that a special type 

 of immunity can be developed against the aggressins. 



