CHAPTER XXXIX. 
THE MICRO-ORGANISM OF SMALLPOX AND COWPOX. 
No bacteria have been found in smallpox which 
seem to have any relation to the disease except as 
secondary infections. The same is true of vaccinia. 
In both the smallpox and vaccinia papules, vesicles, 
and pustules, L. Pfeiffer and others have constantly 
found small, homogeneous bodies in the epithelial cells 
surrounding the lesions. These little bodies are in the 
cell substance, not in the nucleus, and usually but one 
or two exist in any one cell. They are regularly 
missed in the skin when vaccination has failed, and 
also in similarly appearing papules and pustules in 
pyzmia, acne, etc. They apparently belong to the 
class of protozoa, and from their constant presence are 
believed to be the probable specific micro-organisms of 
both diseases. They are at first about double the size 
of the staphylococcus and increase to double that size 
(see Fig. 87, p. 651). Similar bodies have been noted 
in the blood. In a great many specimens of skin from 
cases of variola and vaccinia examined by Williams in 
the health department laboratories these bodies have 
never been entirely missed in the epithelial cells sur- 
rounding the lesions 
The Connection Between Smallpox and Cowpox. The 
inoculation of the virus of smallpox into calves 
produces, when successful, in the first series moderate 
