PROTOZOAN-LIKE BODIES IX SMALLPOX 525 



ficial, but brings a small amount of blood. An area as small as speci- 

 fied is less likely to become infected than a larger one. The scarifica- 

 tions should be separated from each other by an interval of at least 

 one-half to three-quarters of an inch. After they have been made 

 they should be. dried with a sterile towel or with sterile cotton and 

 rubbed with the charged slips. One to two slips, depending on the 

 amount of virus each slip holds, should be sufficient for vaccinating 

 each vesicle. 



COLLECTION. On the fifth or sixth day, depending upon the rate 

 of development of the vaccine vesicles, they should be ready for col- 

 lection. The entire shaved area is washed with sterile water and sterile 

 cotton, and the crusts are picked off. The soft, pulpy mass remaining 

 is then curetted off with an ordinary steel curette and the pulp placed 

 in a sterilized vessel. After the curettage, serum exudes from the torn 

 base of the vesicle, and ivory slips may be charged in this. The pulp 

 should be mixed with from two to three times its weight of glycerin 

 and water, equal parts, and this is done most effectively by passing the 

 mixture between the rollers of a Doring mill. The more watery the pulp, 

 especially if it is not to be used immediately, the smaller should be the 

 proportion of glycerin. The emulsion so produced can then be put up 

 for issue in vials. The slips charged with the serum from the calf may 

 also be used for vaccinating. Capillary tubes require especial means of 

 filling, and small vials filled and corked answer the purpose admirably. 



PROPAGATION. Subsequent animals may be vaccinated in any one 

 of the three ways: (a) slips may be charged from typical vesicles on 

 primary vaccinations, just as with the first calf, and used for seed virus; 

 (6) slips charged with the serum from the calf may be used to vaccinate 

 a second calf; (c) the glycerinated emulsion may be used to vaccinate 

 succeeding calves, but in the last case it is necessary to keep the emulsion 

 a varying length of time often two or three months before it is fit 

 for use in vaccination of the calf, since the employment of fresh 

 glycerinated pulp on a succession of calves leads to prompt degenera- 

 tion of the vaccine and to the production of infected vesicles. 



Care of the Calves. All bedding is avoided and an exclusively milk 

 diet given; thus much of the otherwise unavoidable dust is done away 

 with. 



Laboratory. The laboratory should consist of at least three rooms: 

 (a) stable; (6) operating-room; (c) laboratory-room. It should be 

 possible to make and keep all the rooms clean. The stable and oper- 

 ating-room should be flushed with a hose and hot water daily. Excreta 

 should be removed immediately. The calves can be kept clean if 

 they stand on a raised and perforated platform, which is so short that 

 the defecations cannot fall on it, and if they have no bedding. They 

 must be fastened to keep them from licking the scarifications. In the 

 health department, when a calf is removed, its stall and platform are 

 scoured with a brush and sodium carbonate solution. The stable 

 should he provided with a shovel, broom, hose, currycomb, mane brush, 

 cord, and with halters, buckets, scrubbing brushes, and sponges. The 



