46 



to it, and in the case of the donkey it is mostly recoverable. 

 It has recently been artificially produced in fish. It may be 

 said to be the most widespread disease we have in domesti- 

 cated animals, though somewhat rare in their wild state. 



There is no longer any doubt about the bacteriological 

 identity of all these forms of tuberculosis in the different 

 animals. It was at one time thought that the bacillus in tuber- 

 cular fowls differed from that found in animals, but it is now 

 generally believed that any slight difference that may exist 

 can be accounted for by the different soil on which the bacillus 

 is reared. 



Wherever man goes we find tuberculosis, and where human 

 beings are most crowded together, there the mortality is 

 highest, No country is free from it, but the Faroe Islands, 

 Iceland, Hebrides of Scotland, and the Highlands of Switzer- 

 land enjoy a marked relative immunity. 



In many parts of the vast space of Africa, as in the Upper 

 pai't of the Nile, it is almost unknown. In Algeria the tree 

 Arabs are not affected, while those in captivity readily con- 

 tract the disease. It is prevalent in those who live in the 

 heat of India or Australasia, as well as amongst those who 

 are subjected to the colds of Canada and many parts of 

 America, where it is said to be on the increase. 



It is not therefore confined to any particular country, but, 

 speaking generally, it is most prevalent in countries within 

 the temperate zone, and especially amongst the most densely 

 populated parts of these countries. 



With its distribution climate would seem to have very 

 little to do, but some observers hold it is more severe and 

 rapid in tropical (India, China, and Japan) than in temperate 

 regions. 



All are agreed, however, that a moist, damp atmosphere is 

 decidedly favourable to its prevalence. How this acts is not 

 yet determined. It may have a direct action on the life his- 

 tory of the bacillus, or an indirect action by a relaxing effect 

 upon the mucous membranes. 



Certain seasons of the year have some influence over the 

 prevalence. In Britain the maximum of phthisis is in March, 

 April, and May, with a minimum in August, September, and 

 October. The maximum of tabes mesenteric is, however, in 

 July and August. It has a distinct relationship to the tem- 

 perature, being most prevalent during the diarrhoea season. 

 The minimum is in December, January, and February. 



In Australasia the maximum occurs at different seasons in 

 the various colonies. 



No race of people are exempt, but the Jews seem to enjoy a 

 comparative immunity. 



