EXPERIMENTS IN VACCINATION AGAINST ANTHRAX. 7 



which is then followed in from 14 to 1G days by repeated bleedings. 

 Thus, in the period of a year, the same animals may be bled 10 to 

 11 times, and such animals can be used in this way for several years, 

 alternating the injections with the bleedings, provided they are kept 

 in a well-nourished and healthy condition. 



In order to obtain the largest possible yield of serum from the 

 blood drawn into the glass cylinders a weight is attached to the same 

 and released onto the clotted blood in about 12 hours after being 

 drawn. The diameter of the weight is about half an inch less than 

 the cylinder and its weight is about 2 pounds. In about 24 hours 

 the clear serum is then siphoned into sterile bottles and preserved 

 with 0.5 per cent of carbolic acid. If proper precautions have been 

 practised, it is not necessary to pass the serum through Berkefeld 

 niters ; however, if there is the slightest doubt as to its sterilit}', it is 

 desirable to filter the serum before bottling. It is advisable to dis- 

 tribute the serum in various-sized brown bottles, which should be 

 securely corked and paraffined. 



STANDARDIZATION OF THE SERUM. 



The testing of the serum must be carried out primarily to determine 

 its potency. It is to be regretted that for this purpose there are no 

 accurate or definite methods known, and it is almost impossible to 

 establish the absolute protective value of the serum, because the 

 animals on which it is being tested are so very highly susceptible to 

 the disease. Nevertheless, it is possible to establish a relative value 

 for all practical purposes through laboratory experiments, and some 

 investigators believe that rabbits are best adapted for the purpose. 

 The standardization test as recommended by Sobernheim is still em- 

 ployed by various investigators. This test is carried out as follows : 



Potency test for anthrax serum {Sobernheim). 



Rabbit. 



First injection. 



Second injection. 



A.. 



B 



C 



D 



E 



F (control). 



G (control). 



2c.c. of immune serum (intravenous) 



3 c. c. of immune serum (intravenous) 



4 c. c. of immune serum (intravenous) 



5 c. c. of immune serum (intravenous) 



6 c. c. of immune serum (intravenous) 



0.001 loopful of a suspension of virulent 



anthrax bacilli in 1 c. c. of 0.7 per cent 

 sodium-chlorid solution. 

 do 



Follow immediately by a subcutaneous 

 injection of 0.001 loopful of a suspension 

 of virulent anthrax bacilli in 1 c. c. of 0.7 

 per cent sodium-chlorid solution. 



] 



According to extensive experience, a serum is considered potent 

 and satisfactory for immunization purposes when at least two of 

 the five rabbits given the serum remain alive and the others die 

 later than the control animals. Should more than the two animals 

 remain alive, while the control animals die in about 48 hours, the 



