PREVENTIVE MEDICINE 257 



the disease. Cases have also been described in the horse by Ganter,* 

 Hess and Semmer, but are open to doubt. Other animals, includ- 

 ing man, are immune. 



Black quarter occurs sporadically with a marked regional dis- 

 tribution. In some parts of the country the disease is practically 

 unknown, while in other parts certain districts, farms, or even 

 particular fields show a number of cases annually, and in this way 

 the expression " black-quarter farms " has come into use. It thus 

 appears that the organism like the tetanus bacillus is saprophytic 

 in the soil of certain localities, and its existence is normally main- 

 tained in this way and not by multiplication within the animal body. 

 It is important to remember, however, that a single case of the 

 disease, if carelessly handled after death, is capable of producing 

 very dangerous local contamination of the soil. 



According to Butcher f cases are usually met with in late 

 autumn, winter, and again in the spring, though they may be seen 

 at any time of the year. The disease is rare in very young calves 

 owing to the smaller risk of infection, and is most commonly met 

 with in animals between the ages of six months and two years, 

 though susceptibility varies within wide limits. In adult cattle it 

 is rarely seen, this being probably due to susceptibility naturally 

 diminishing with age. The notion that the disease was more liable 

 to appear in animals receiving very rich diet or undergoing forced 

 feeding is now happily generally abandoned, the idea having no 

 foundation in fact. The sheep has no special susceptibility accord- 

 ing to age. 



The manner in which animals become infected is in a measure 

 uncertain. Probably it occurs by ingestion in spite of the well- 

 known fact that the disease has never been produced experiment- 

 ally by feeding, even with enormous doses of the organism in 

 culture. Some suppose that association with other organisms 

 within the intestinal canal is necessary. Probably in certain cases 

 animals become infected by inoculation, and M'Fadyean has noted 

 small enzootics of the disease occur in sheep after shearing. The 

 period of incubation is generally 3 days, but does not exceed 5 

 days. J 



The disease has a very high mortality, and extremely few cases 

 which have shown a well marked black-quarter " tumour " recover. 

 It is stated, however, that at times the symptoms shown by the 

 animal may be so slight as to escape notice, and that this occurs 

 especially in herds in which the losses are frequently considerable. 

 * Journ. Comp. Path., 1891, Vol. IV., p. 70, Abs. 

 t/orn. Comp. Path., 1891, Vol. IV., p. 59. 

 t Hutyra and Marek, Spec. Path., Vol. I., p. 47, Trans. 



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