IMMUNITY TO DISEASE 107 



tuberculous lesion, active or obsolete, is as high as 75. . . . 

 If, as has been done in Ribbert's laboratory, a systematic 

 inspection is made for the purpose, tuberculous lesions 

 are found in practically 100 per cent, of the bodies of 

 adults." 1 Nageli laid down the principle that "every 

 adult is tuberculous," and Bertzke, discussing this, states 

 that of the adults that have died in hospital some 70 per 

 cent, show evidence of tuberculous changes. 2 Moreover, 

 when a person suffering from tuberculosis leaves Northern 

 Europe and goes to South Africa or some other suitable 

 climate, he generally recovers. Even without leaving the 

 country in which the disease has been acquired, recovery 

 must be very frequent, even in comparatively advanced 

 stages. " These lesions in the majority of cases are not 

 phthisis in an early stage manifested by small disseminated 

 foci ; they are cicatrices of large foci ; sometimes of wide 

 completely cicatrised cavities. Phthisis, therefore, is curable 

 even in its most advanced stages." 3 In races where there has 

 been no selection, however, individuals form a suitable soil in 

 which the bacilli can flourish and multiply under conditions 

 where the most susceptible of individuals in Northern 

 Europe would be able either to resist the infection, 4 or 

 would eliminate the bacillus after it had established itself. 



1 Osier, W., The Principles and Practice of Medicine, 5th edition, London, 

 Appleton & Co., 1904. 



2 Bertzke, " Uber Haufigkeit und Infectionswege der Tuberculose," Tuber- 

 culosis, April 1906, vol. v., No. 4, Berlin. 



3 Brouardel, Trans. British Congress on Tuberculosis, vol. i., W. Clowes, 

 London, 1902. 



* Dr. Cleasby Taylor, who has practised for many years in Las Palmas, 

 informs me that when a native of the Canary Islands is stricken with tuber- 

 culosis, many members of his family also die of it in a short time. This is 

 so marked, that lie has known of whole households practically exterminated. 

 The Spaniards colonised the islands more than four hundred years ago, and 

 cannot then as a race have been subjected to anything like the selection with 

 regard to tubercle that has been the lot of more northern races. They inter- 

 married to some extent with the natives, so that the present race is a mixed one. 

 This race has not been subject to selection since that time, and the tubercle 

 bacillus has been carried there since the islands have been used as a health 

 resort by tubercular patients. The cases of the aborigines in North America, 

 Australia, and New Zealand are still more striking. They become infected 

 easily and always die. 



