APPENDIX E. cxxxvii 



limitations. Facts abound, and speak most plainly to those 

 who will read them dispassionately. Referring to the pre- 

 valence of yellow fever on the coast of Brazil, Dr. McKinlay * 

 wrote : — 'Almost every person who joined the Vestal during 

 the prevalence of fever was affected by it; but no person 

 leaving her, under the disease, communicated it to another, 

 in another place.' That is, as he afterwards explained, so 

 long as the affected persons went to a healthy place in which 

 the disease was not prevailing. 



Occurrences of this kind are most notorious ; and, when 

 an epidemic of yellow fever occurs on land, it has often been 

 found that there are boundaries at no great distance from the 

 tainted district where the disease has not, and to which it 

 will not, spread ^. The value of migration from the affected 

 region is a matter of history, and the circumstances which 

 have revealed it have all the value of experiments conducted 

 upon a large scale. 'During the epidemic of 1800, at Cadiz, 

 14,000 persons left that city when the disease became sus- 

 pected. These people fled to the country, where they re- 

 mained free from the epidemic; while of the 57,499 who 

 remained, 48,520 were attacked, of whom 6,884 lost their 

 lives.' And again we read ^ : — ' It was calculated that from 

 Barcelona, in 182 1, about 80,000 persons fled; and, except 

 some who departed with the disease already upon them, 

 or who were on the eve of being attacked, all remained 

 exempt from the reigning malady.' But when individuals 

 from an infected district pass into a region where conditions 

 prevail which are favourable to its spread, or which are them- 

 selves capable of engendering typhiis or other fevers, then 

 yellow fever appears to be a contagious disease. A good 



^ 'Monthly Journal of Medical Science,' November, 1852, p. 425. 

 2 See ' Med.-Chir. Rev.,' 185J, vol. xiii. p. 338. 

 ^ ' Second Report on Quarantine,' etc., p. 202. 



