152 



LABORATORY COURSE IN SERUM STUDY 



deteriorate readily in solution. They are known as hsemotoxins 

 and their injection in suitable doses into animals leads to the pro- 

 duction of antitoxins whose specific protective action can be 

 demonstrated in vitro. 



These hsemotoxins also have a hsemolytic action in the body, 

 although they play a smaller role than the other toxic components 

 (neurotoxin, for instance, in the case of tetanus). Their in vivo 

 haemolytic effect is probably greatly hindered by the protective 

 power which normal serum possesses when in sufficient concen- 

 tration. 



I. DETERMINATION OF MINIMAL LAKING DOSE OF TETANUS TOXIN 



Tetanus toxin (either a recently prepared filtrate or a toxin precipi- 

 tated with ammonium sulphate and preserved in the dry state and made 

 up to 1 per cent solution in 0.9 per cent saline) l is tested as follows : 



Incubate one hour at 37 C., and observe haemolysis. 



II. TlTRATION OF ANTITETANOLYSIN IN IMMUNE HORSE SERUM 



(TETANUS ANTITOXIN) 



1 A preliminary trial by the instructor is desirable before the toxin is given 

 out to the class, as the quantities of toxin given in the table may have to be 

 modified. 



