150 



LABORATORY COURSE IN SERUM STUDY 



and the following series of dilutions accurately made from this in test 

 tubes : 



1 c.c. of each dilution is then mixed in a Rosenau syringe with 2 c.c. 

 of diluted toxin, the mixture allowed to stand one hour at room tempera- 

 ture, injected subcutaneously into a guinea pig in the manner described 

 for determining the MLD, the syringe washed with salt solution and the 

 pigs numbered and carefully observed. Should pigs receiving dilutions 

 1 to 3 survive for five days, and the pigs receiving the higher dilutions 

 die in two to five days the serum in question would contain 260 units 

 per c.c. Guinea pigs which die should be autopsied and the character- 

 istic lesions found. 



To provide a margin of safety in testing commercial sera it is cus- 

 tomary to consider the smallest unit which serves to protect the pig as a 

 unit, in this case -^ of 1 c.c., which means that there are 240 units 

 to the cubic centimeter. 



Materials needed for III, Determination of unknown antitoxin : 



Antitoxin. , 



Diphtheria toxin whose M. L. Dose and L-f Dose are exactly known. 



Precision syringes. 



12 guinea pigs of approximately 250 grams weight. 



LESSON XXIII 



TETANUS TOXIN 



TETANOLYSIN AND ANTITETANOLYSIN 



MANY bacteria, for instance tetanus bacillus, Staphylococcus, 

 various vibrios, Bacillus megatherium and Bacillus proteus, 

 develop, in culture media, substances which are capable of laking 

 red cells. These substances are relatively thermolabile and 



