662 DISEASES CAUSED BY FILTRABLE VIRUS 



scratches themselves become slightly raised and papular, and within four 

 or six days typical vaccinia 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 thor- 

 oughly removed by subsequent washing with sterile water. Crusts, if 

 present, are then carefully picked off and the entire contents of the vesi- 

 cle, 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 glyce- 

 rin fifty parts, water forty-nine parts, and carbolic acid one part. 1 Ger- 

 man 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 trit- 

 urating 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 curettage 

 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 2 inoculate rabbits upon the inner surfaces of the 

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

 ment and extensiveness of the resulting lesions. Guerin 3 has estimated 

 the potency of virus quantitatively by a method depending upon the 

 inoculation of rabbits with a series of dilutions. Beginning with a mix- 

 ture containing equal weights of glycerin and vaccine pulp, dilutions are 

 made with sterile water ranging from 1 in 10 to 1 in 100. Rabbits 

 are shaved over the skin of the back and 1 c.c. of each of these dilu- 

 tions is rubbed into the shaved areas. Fully potent virus should cause 



1 HuddUston, quoted in Park, "Pathogenic Bacteria," N. Y., 1908. 



2 Calmette and Guerin, Ann. de 1'inst. Pasteur, 1902. 



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



