530 VARIOLA 



then of vesicles and finally of pustules. It is common to 

 horses, cattle, and man. Sheep suffer from a like or similar 

 disease. Other species are said to be occasionally attacked. 



§ 417. History. Small pox in man has existed from 

 very early times. It is reported to have been mentioned in 

 the Chinese records of 1122 B. C. It was quite fully and 

 accurately described by an Arabian physician (Rhazesin) in 

 the early part of the tenth century. The disease in animals 

 has been known for many years. Sheep pox is reported by 

 Joubert to have existed in 1567. Cow pox has existed for 

 centuries but since Jenner's discovery of vaccine it has received 

 more attention. The same is true of horse pox. 



The etiological relations of the pox of man and animals 

 to each other are not yet clearly enough demonstrated. The 

 constantly agreeing anatomical structure and the like develop- 

 ment of the pustules characteristic of the disease speaks for the 

 etiological identity of the various forms of pox, but yet what 

 we know concerning their different infectiousness especially 

 the susceptibility to them, as well as the appearance of the 

 disease, accords little with this identity. 



While in man and sheep the disease usually appears with 

 severe general symptoms and with a diffuse pock eruption, the 

 eruption is confined always in cattle and almost always in 

 goats to single places on the body, and in its development is 

 accompanied by very mild general symptoms. The disease 

 among men on the one hand and sheep on the other spreads 

 very easily, providing the acquired immunity of the individual 

 does not interfere, while on the contrary among other animals 

 the spread even in the case of favorable conditions becomes 

 important only within narrow limits. 



Doubtless the relations between the pox of men and cattle 

 are very close. The latter is very easily inoculated into man 

 yet the inoculation always produces a single eruption limited 

 to the place of inoculation and never a general affection giving 

 evidence of variola. On the contrary human pox is much less 

 safely transmitted to the cow. In a part of such cases there 

 appear in the cattle characteristic pocks at the place of inocu- 



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