DISEASES OF UNKNOWN ETIOLOGY (355 
the epithelia of both smallpox and vaccinia lesions and in experi- 
mental lesions in the cornea of rabbits as well, which he regards as 
protozoa, and to which he gave the name Cytorhyctes variola^. Coun- 
cilman, Magrath and Brinkerhoff^ have studied these vaccine bodies 
in detail and incline to the view that they are parasites specific for 
the disease. Calkins- has construed the various forms of the cell 
inclusions to be distinct stages in the life history of a protozoal i)arasite. 
The protozoal nature of the "vaccine bodies" is not universally con- 
ceded, and the conservative statement of Ewing^ that they may be 
regarded as degenerative phenomena characteristic for the disease is 
widely accepted at the present time. 
Fig. 100. — Guarnieri cell inclusion bodies. 
The close relationship between smallpox and vaccinia (cowpox) 
has been recognized since Jenner's* classical researches published in 
1789; he showed experimentally that a successful inoculation of man 
with cowpox virus protected the individual against infection with the 
virus of smallpox. 
The change which the smallpox virus undergoes during passage 
through calves is not definitely known, but Councilman, Magrath, 
Brinkerhoft' and others are of the opinion that the smallpox A'irus is 
somewhat widely distributed in the viscera and different organs of 
the body (in man) ; passage of the virus through cah'es so modifies its 
activities that it localizes rather specifically in pavement epithelium. 
The relatively insignificant local lesions of vaccinia in contrast to the 
general distribution of the eruption and lesions of smallpox are in 
harmony with this view. 
.Tenner's remarkable studies upon the immunity to smallpox that 
1 .lour. Med. Res., 1904, 11. 12. 
2 Ibid., p. 1.36. ■' Ibid., 1904, 13, 233. 
•• An Inquiry Into the Causes and Effects of the Variolae Vacciniae, a disease discovered 
in some of the Western Counties of England, particularly Gloucestershire, and Known 
by the Name of the Cow Pox. London, Sampson Low, 1789. (See Epoch-making 
Contributions to Medicine, Surgery and Allied Sciences, Camac, Saunders and Co.) 
