Group II. 



ACUTE EXANTHEMATOUS INFECTIOUS DISEASES 



1. Pox. Variola. 



{Pockenkranklieif [Genywn]; Variole [French]; Vajuolo 

 [Italian].) 



As pox are designated acute febrile, infectious diseases, 

 which usually take a typical course and are characterized by 

 a peculiar vesico-pustular exanthema which develops on the 

 skin, either over the entire surface of the body or only over 

 certain parts. In its first form the disease occurs in man, in 

 sheep, and, although more rarely, in goats and hogs ; in cattle 

 and horses it is almost invariably observed only as a benign 

 local affection. 



Accordingly only sheep pox, and to some extent also pox 

 of goats and swine, are of any economic importance, inasmuch 

 as sheep pox usually occurs in an epizootic form and causes 

 notable losses. 



Etiology. All that is known at the present time regarding 

 the virus of variola in the various species of animals and in 

 man, is that in filtration of the contents of the vesicles under 

 high pressure it passes through moderately dense porcelain 

 filters, and therefore probably belongs to the ultra-microscopical 

 micro-organisms. 



The very numerous bacteriological investigations which were made 

 principally with the infectious material from human and from cow 

 pox, have up to the present time failed to give positive results. For- 

 merly the causative agent of the disease was believed to be a bacterium 

 (Kleber, Simon, Hallier, Cohn, Toussaint, Klebs, Voigt, Garre, ]\[arrotta 

 and others), in recent times it has been considered as a protozoon. 

 Pfeiffer & Eieck observed in the lymph of the vesicles, spherical bodies 

 containing a nucleus, and of a greenish lustrous color, with a move- 

 ment somewhat resembling that of amoebae. They considered these 

 bodies as parasites belonging to the species of protozoa, or to the class 

 of raonocystidea, naming them sporidium vaccinale. Fnnck on the 

 other hand considers them as spores of these parasites, while Guarnieri 

 attributes the causative role to certain contents of epithelial cells 

 (Cytorhyctes vaccinae et variolae), which he believed to have cultivated 

 on the cornea of rabbits ; the same view is also accepted by Siegel. 

 Other authors however consider them as parts of cells, or as remains 

 of polynuclear leucocytes which have penetrated into the epithelial cells 

 (Salmon, London, Schrumpf, Miihlens & Hartmann). Calmette & 

 Guerin are inclined to regard as the causative factor of pox, extremely 



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