MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 857 



The microorganism of bovine pleuro-pneumonia is generally classed 

 among the filtrable viruses, though unlike some organisms of that 

 class it has been cultivated artificially and is just visible at a magni- 

 fication of 2,000 diameters. The artificial cultivation of this virus was 

 accomplished by Roux and Nocard through the use of the very in- 

 genious "collodion sac method." A small amount of virus from a 

 diseased cow was placed within a small thin- walled sac of collodion; 

 after being hermetically sealed the sac was placed in the peritoneal 

 cavity of a rabbit where it remained for several weeks. At the end of 

 this time the unbroken sac was removed and the previously clear fluid 

 within was found to be slightly opalescent. Microscopic examination 

 revealed numberless minute motile bodies so small, however, that their 

 exact form could not be determined. Later the organism was suc- 

 cessfully cultivated outside of the animal body in a specially prepared 

 bouillon. These cultures produced the disease when inoculated into 

 susceptible cattle. When the virus is diluted it will pass through the 

 Berkefeld and Chamberland F cylinders, but not through the Chamber- 

 land B cylinder. 



COWPOX, HORSEPOX, AND SHEEPPOX* 



Variola refers to a condition or disease in man and animals, charac- 

 terized by fever and the appearance of skin eruptions which succes- 

 sively assume the form of papules, vesicles and pustules. The disease 

 is frequently found in the human species (smallpox), cattle (variola 

 vaccinia, cowpox), horses (variola equince, horsepox) and sheep (variola 

 ovina, sheeppox). It is possible that some other species may be 

 susceptible. 



On account of the fact that vaccination of man with virus from cases 

 of cowpox affords remarkable protection against smallpox, it appears 

 reasonable to believe that cowpox virus or smallpox vaccine is a 

 modified form of smallpox virus. This fact, together with the occa- 

 sional positive results of various experiments in which other species 

 of animals have at times evidenced susceptibility to cowpox virus, 

 strongly suggests the possible etiological relationship of the diseases in 

 different species to each other and to smallpox in man. However, 

 conclusive proof supporting this suggested relationship does not exist. 

 The specific causative factor of smallpox or of cowpox is not known. 



* Prepared by W. E. King. 



