Variola : Sheeppox. 349 



This relative immunity is still more decided when we come to 

 animals of other genera. Though the latest results of research 

 seem to identify the sporidia found in the different forms of 

 variola, yet the long habit of living in an environment found in 

 the ovine race unfits the germ for pathogenic life in various other 

 genera that have their own variolse. Sacco and Villain reported 

 inoculations from sheep to man, but as the first was experimenting 

 with variola at the same time, and the second did not test his 

 pustules by reinoculation the results are not convincing. Kiichen- 

 meister had a general eruption in sheep after intravenous injec- 

 tion of variola of man, but failed to test it by reinoculation. 

 Voisin and Nocard on the other hand were uniformly unsuccessful 

 in attempts to convey sheeppox to man, and the handling of 

 variolous flocks from time immemorial must have led to many 

 cases in man, had he been appreciably receptive. It is virtually 

 the same with cowpox. Huzard vaccinated 2,000 sheep without 

 producing immunity from sheeppox. Voisin had precisely similar 

 results. He further inoculated infants with sheeppox, and later, 

 successfully, with vaccine lymph. ' 



It does not follow that these genera would be insusceptible 

 under all conditions. Yet the failure to immunize against each 

 other would argue a wider divergence of sheeppox and cowpox, 

 than of smallpox and cowpox, or than of bovine and avian 

 tuberculosis. 



Galtier failed to inoculate sheeppox on rabbits or Guineapigs, 

 yet Jourdan, records a de.structive outbreak in the Alps, in hares, 

 kept in the same places with variolous sheep. 



Accessory External Causes. All unwholesome conditions of 

 life, and especially overcrowding, filth, starvation, and neglect 

 contribute to the extension of the infection. Still more so, the 

 importation of sheep, whether in the parks of armies, or in the 

 channels of trade, by rail, or steamboat, through stockyards or 

 markets. 



The virus is possessed of unusual vitality, and in the dried 

 condition, secluded from air and light will remain virulent for an 

 indefinite period. Hence the danger of wool, and dried sheep- 

 skins. Even in the moisture of an ordinary shed it has retained 

 its infectiveness for five or six months. The sheep that has re- 

 covered from the affection may transmit the disease to others for 



