654 APPENDIX. 
Collection. On the fifth or sixth day, depending upon 
the rate of development of the vaccine vesicles, they 
should be ready for collection. The entire shaved area 
is washed with sterile water and sterile cotton, and the 
crusts are picked off. The soft, pulpy, remaining mass 
is then curetted off with an ordinary steel curette and 
the pulp placed in a sterilized vessel. After the curet- 
tage 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. A watery pulp, especially 
if it is not to be used immediately, should have the 
smaller proportion of glycerin. The emulsion so pro- 
duced 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 to vaccinate the calf, because the use of 
fresh glycerinated pulp on a succession of calves leads 
to prompt degeneration of the vaccine and to the pro- 
duction of infected vesicles. 
