276 



DEFINITE ACTION OF THE 



Chap. XXIII. 



according to Liebig 17 the blood of men with different complexions 

 though inhabiting the same country, emits a different odour. 



Diseases peculiar to certain localities, heights, or climates, may be here 

 briefly noticed, as showing the influence of external circumstances on the 

 human body. Diseases confined to certain races of man do not concern 

 us, for the constitution of the race may play the more important part, and 

 this may have been determined by unknown causes. The Plica Polonica 

 stands, in this respect, in a nearly intermediate position ; for it rarely affects 

 Germans, who inhabit the neighbourhood of the Vistula, where so many 

 Poles are grievously affected ; and on the other hand, it does not affect 

 Eussians, who are said to belong to the same original stock with the 

 Poles. 18 The elevation of a district often governs the appearance of 

 diseases ; in Mexico the yellow fever does not extend above 924 metres ; 

 and in Peru, people are affected with the verugas only between 600 and 

 1600 metres above the sea; many other such cases could be given. 

 A peculiar cutaneous complaint, called the Bouton d'Alep, affects in Aleppo 

 and some neighbouring districts almost every native infant, and some few 

 strangers ; and it seems fairly well established that this singular complaint 



certain waters. In the healthy little island of 

 St. Helena the scarlet-fever is dreaded like the Plague ; analogous facts 

 have been observed in Chili and Mexico. 19 Even in the different depart- 

 ments of France it is found that the various infirmities which render the 

 conscript unfit for serving in the army, prevail with remarkable inequality, 

 revealing, as Boudin observes, that many of them are endemic, which 



depends on drinking 



otherwise would never have been suspected. 20 Any one who will study 

 the distribution of disease will be struck with surprise at what slight 

 differences in the surrounding circumstances govern the nature and 

 severity of the complaints by which man is at least temporarily affected. 



such changed conditions, if acting 



The modifications as yet referred to have been extremely 

 slight, and in most cases have been caused, as far as we can 

 judge, by equally slight changes in the conditions. But can it 

 be safely maintained that 

 during a long series of generations, would not produce a marked 

 effect ? It is commonly believed that the people of the United 

 States differ in appearance from the parent Anglo-Saxon race ; 

 and selection cannot have come into action within so short a 

 period. A good observer 21 states that a general absence of fat, 



V ' Organic Chemistry /Eng.translat., taken from Dr. Boudin's 'Geographic 



1st edit., p. 369. 



18 Priohard, 'Phys. Hist, of Mankind/ 

 1851, vol. i. p. 155. 



19 Darwin, ' Journal of Eesearclies,' 

 1845, p. 434. 



2U These statements on disease are 



et de Statistique Medicales/ 1857, torn. 

 i. p. xliv. and lii. ; torn. ii. p. 315. 



21 E. Desor, quoted in the ' Anthrop. 

 Rev./ 1803, p. 180. For much confirma- 

 tory evidence, see Quatrefages, 'Unite 

 de TEsp'jee Humaine/ 1861, p. 131. 





