156 



LABORATORY COURSE IN SERUM STUDY 



LESSON XXIV 

 TOXINS OF HIGHER PLANTS AND ANIMALS 



MANY of the higher plants and animals produce toxins resem- 

 bling in every way the toxins of bacterial origin. The property 

 which is essential for the identification of such substances as toxins 

 is the possibility of producing antitoxins for them. The other 

 properties, such as the extraordinary potency and thermolability, 

 are less essential. Most of them have more than one toxic com- 

 ponent, like many of the bacterial toxins (for instance, tetanus 

 toxin). Thus beside the effect on the nervous system and blood 

 vessels snake poisons are hsemolytic, and ricin, a powerful toxin 

 derived from the castor bean, is hsemagglutinative. 



Human and guinea pig cells are susceptible to laking by 

 cobra venom in the absence of serum or lecithin. Sheep and ox 

 cells are highly resistant. The addition of lecithin or of suitable 

 serum, however, makes the insusceptible cells again susceptible 

 to laking by the venom. 



Kyes at first supposed that the lecithin " activated " the hsemo- 

 lysin of the cobra venom by an action analogous to that of com- 

 plement in the case of the specific hsemolysins. Later researches, 

 especially those of von Dungern and Coca, showed that the venom 

 contained a lipoid-splitting enzyme or lipase which acted upon the 

 lecithin of the cell membrane or the lecithin contents of the serum 

 and liberated split products which possessed haemolytic action. 



Set up the following tests : 



HjEMOLYTTC EFFECT OF COBRA VENOM 



Incubate one hour at 37 C., making observations every 15 minutes, 

 and note whether the occurrence of haemolysis confirms the statements 

 made above. 



