SMALLPOX AND COWPOX. 653 
Animals. The preferable animals are female calves, 
from two to four months of age, in good condition and 
free from any skin disease. These can be vaccinated 
on the posterior abdomen and inside of the thighs easily 
by placing them on an appropriate table. It is possible 
that on account of the character of the available supply 
older animals may be desirable, but the calves take 
more typically and are more easily handled. When 
an animal is too old to be thrown and held easily it 
may be vaccinated on the rump, each side of the spine; 
but the skin there is tougher, and the resulting virus, 
though efficient, is not so easily emulsified. 
Vaccination. The calf should be cleaned thoroughly, 
including the feet and the tail, and the hair should be 
clipped from the end of the tail. The posterior abdo- 
men and insides of the thighs are then shaved and the 
skin beneath washed in succession with soap and water, 
sterilized water and alcohol, and then dried with a 
sterile towel. On this area there are then made about 
one hundred scarifications, each from one-quarter to 
one-half of an inch on a side. The scarification is 
made most easily by cross-hatching with a six-bladed 
instrument, the blades being about one-thirtieth of an 
inch apart. The scarification is superficial, but brings 
blood. An area as small as specified is less likely to 
become infected than a larger one. The scarifications 
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 cotton and rubbed with the charged slips. One 
to two slips, depending on the amount of virus each slip 
contains, should be sufficient for vaccinating each ves- 
icle. 
