GENERAL CONSIDERATION OF FILTRABLE VIRUS 897 



hours the scratches themselves become slightly raised and papular, 

 and within four or six days typical vaccina vesicles have usually 

 developed. 



To obtain the vaccine from such lesions, the entire operative 

 field is carefully washed with warm water and soap, followed by 

 sterile water. In some cases two per cent lysol is employed, but 

 must again be thoroughly removed by subsequent washing with 

 sterile water. Crusts, if present, are then carefully picked off and 

 the entire contents of the vesicle, sticky serum, and pulpy exudate 

 removed by the single sweep of a spoon-curette. The curetted 

 masses are caught in sterile beakers or tubes and to them is added 

 four times their weight of a mixture of glycerin fifty parts, water 

 forty-nine parts, and carbolic acid one part. 15 German workers 

 prefer a mixture of glycerin eighty parts, and water twenty parts, 

 omitting the use of carbolic acid. The glycerinated pulp is allowed 

 to stand for three or four weeks in order to allow bacteria, which 

 are invariably present, to die out. After preservation for such a 

 length of time, moreover, thorough emulsification is obtained more 

 easily than when this is attempted immediately after curettage. At 

 the end of three or four weeks, the glycerinated pulp is thoroughly 

 triturated, either with mortar and pestle or by means of specially 

 constructed triturating devices. Pulp so prepared should remain 

 active for at least three months if properly preserved in sealed tubes 

 in a dark and cool place. 



From the serum oozing from the bases of the lesions, after curet- 

 tage, bone or ivory slips may be charged for vaccination with dry 

 virus. The glycerinated pulp is put up in small capillary tubes, 

 sealed at both ends, and distributed in this form. Park states that 

 a calf should yield about 10 grams of pulp (which when made up 

 should suffice to vaccinate 1,500 persons), and. in addition about 

 200 charged bone slips. 



The virus may be tested for its efficiency by a variety of methods. 

 Calmette and Guerin inoculate rabbits upon the inner surfaces of 

 the ears and estimate the potency of the virus from the speed of 

 development and extensiveness of the resulting lesions. Guerin 16 

 has estimated the potency of virus quantitatively by a method 

 depending upon the inoculation of rabbits with a series of dilutions. 



Huddleston, quoted in Park, "Pathogenic Bacteria/' N. Y. 1908. 

 18 Guerin, Ann. de 1'inst. Pasteur, 1905. 



