SYMPTOMS 



533 



one species lost partly or entirely its pathogenesis for other 

 species. 



S 418. Geographical distribution. It has been re- 

 ported in animals from many places in Europe, in northern 

 Africa and Asia. Cow pox has been reported in America. 



§ 419. Etiology. The cause of variola is not known. 

 A number of different microorganisms have been isolated but 

 thus far their discoverers have not been able to reproduce the 

 disease with them. Some investigators believe the cause to 

 be a protozoan which they believe they have found in the tis- 

 sues. The work of Councilman stands foremost in this line. 

 The virus is quite hardy and remains alive for a considerable 

 time if not exposed to direct sunlight. The identity of the 

 disease in horses, cattle, sheep and man has not, therefore, 

 been positively determined, although the results reported by 

 Hine, Simpson, Freyer and others suggest an etiological rela- 

 tionship if not an identity. If the identity is not established, 

 then the diseases in the different species now called variola 

 must be considered as distinct maladies. It seems desirable 

 at this time to consider them under the generic name Variola, 

 treating the disease as found in each species separately. 



§ 420. Symptoms. The symptoms vary somewhat in 

 the different species, but the e.ssential ones are a rise of tem- 

 perature and the appearance of a definite eruption on the skin 

 or mucous membranes. This is at first papular, then vesicular 

 and finally pustular. It is rarely a dangerous affection in 

 animals and often it is very mild. The peculiar symptoms 

 and lesions as recognized in each species of animals are 

 appended. 



§ 421. Horse pox. The eruption occurs on the buccal 

 membrane, nasal mucosa, conjunctiva (rarely), mucosa of 

 generative organs, and upon the skin. In the latter case the 

 pustules may occur over the entire body or be localized in 

 certain regions. The lesions consist of the specific pustules. 

 On the mucosae the pustule begins with the congestion of the 



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