PROPHYLACTIC IMMUNIZATION OR VACCINATION 629 



mass cureted off with a special, spoon-like curet and collected in a 

 sterile vessel. After the curetage, serum exudes from the excoriated 

 base of the vesicle, and ivory tips may be charged in this. The sticky 

 and pulpy exudate is then mixed with four times its weight of glycerin 

 and water (50 per cent, glycerin, 49 per cent, water, 1 per cent, phenol), 

 and this is done most effectively by passing the mixture between the 

 rollers of a Doring mill. The glycerinated pulp is allowed to stand for 

 three or four weeks in order to allow bacteria, which are invariably 

 present, to undergo dissolution. At the end of this time the glycerinated 

 pulp is thoroughly titrated in specially constructed triturating machines, 

 and put up in small capillary tubes, which are sealed, or "vaccine 

 points" may be prepared. If. properly preserved in sealed tubes in 

 a dark, cool place the virus should remain active for at least three months. 



According to Park and Huddleson, 10 grams of pulp and 200 charged 

 slips would be an average yield from a calf, and when made up should 

 suffice to vaccinate at least 1500 persons. Calves vary greatly in their 

 yield of virus. Of two calves vaccinated in exactly the same manner, 

 one may furnish material for 500 vaccinations and the other for 10,000 

 inoculations. 



Testing the Vaccine. The virus may be tested for its efficacy by a 

 variety of methods. Calmette and Guerin 1 inoculate rabbits upon the 

 inner surfaces of the ears and estimate the potency of the virus from the 

 speed of development and the size of the resulting lesions. Guerin 2 

 estimates the potency of virus quantitatively by inoculating rabbits 

 with serial dilutions ranging from 1 : 10 to 1 : 100. Fully potent virus 

 should cause closely approximated vesicles in a dilution of 1 : 500, and 

 numerous isolated vesicles in a dilution as high as 1 : 1000. 



Quantitative estimation of the bacteria in the glycerinated virus 

 is made by the plating method, and the vaccine used only when the 

 numbers of bacteria have been greatly diminished or are entirely absent. 

 The vaccine is also tested for tetanus by injecting relatively large 

 quantities subcutaneously into guinea-pigs and mice. 



Under the Federal Law of July 1, 1902, and the regulations framed 

 thereunder, all firms manufacturing vaccine virus are required by the 

 Secretary of the Treasury to obtain a license before they may sell their 

 products in interstate commerce. The vaccine laboratories are care- 

 fully inspected by an official of the Hygienic Laboratory of the United 

 States Public Health and Marine-Hospital Service; the inspector 

 carries away with him as many samples of virus as he wishes, and addi- 



1 Ann. de 1'Inst. Pasteur, 1902. 2 Ann. de 1'Inst. Pasteur, 1905. 



