1885.] Br. Beck^ Pathological Evolution, 39 



ism. The mechanism by which '^ predispositions," hereditary or 

 otherwise, are determined, and the agencies by which '' resisting 

 power " to infection is developed, would fall under this head. The 

 liying body, it must be remembered, is made up of living cell 

 elements. 



These obey the same laws that living matter elsewhere does, and a 

 constant adaption to surrounding circumstances goes on. That this is 

 so is beautifully illustrated by the ''official documents" upon the 

 annual mortality in the thousand inhabitants at Sierra Leone from 

 1829 to 1836. 



From these it appears that while 410-2 per 1,000 Europeans 

 annually die from " marsh fever," only 2*4 Negroes succumb. This 

 will amply demonstrate what I mean. On no assumption can the 

 disproportion in mortality be explained but that by which the Negro 

 is credited with a special resistance to miasmatic infection. 



This power of resistance can only have resulted from a gradual 

 adaptation to their surroundings of the living cells in successive genera- 

 tions of Negroes, an adaptation which in transmission from father to 

 son became intensified sufficiently to create ultimately an almost 

 absolute immunity from marsh fever. 



On the assumption of such adaptation can almost be explained the 

 occurrence of acute fevers in epidemic form, such as, e.g., small-pox. 

 It is reasonable to assume that when a series of laws, climatic or 

 otherwise, come into operation to favour the development in certain 

 directions of germs outside, that the same laws, reacting upon the 

 human organism, create an adaptation of parts, which for the time 

 determines a susceptibility to infection. 



When these laws change, a reverse process may be assumed to go 

 on, and the epidemics disappear. 



If this were not so, then it would be quite unexplainable why such 

 epidemics as our last small-pox outbreak should ever disappear 

 entirely. AVe know that every person attacked increases in a positive 

 ratio the quantity of poison. When, therefore, an epidemic is at its 

 height, the quantity of infecting material must also be at its 

 maximum. 



Instead of going on, however, a retrogressive development occurs, 

 and the epidemic dies out not only, but also remains away for perhaps 

 a period of years, and then appears again. If this retrogressive 

 development were not there, we should be at an entire loss to account 

 for the fact that there was no spread of small-pox in Cape Town last 

 year when cases from Kimberley were imported, especially when we 

 take this fact in connection with what happened in 1882, when a 

 single case created in the most rapid manner an epidemic which raged 

 over the whole of the Western Province almost. It must be remem- 

 bered that there are always unvaccinated persons in large towns. 



M. Boudiriy in an interesting work on ethnological pathology, 

 writes as follows : — "Elephantiasis, that affection by which certain 

 parts of the body are sometimes deformed in so strange a manner, is 

 found in the Indies and at Barbadoes. 



" In the latter island negroes alone were attacked by this hideous 

 disease till the year 1704. One white was in that year affected by it 

 for the first time. But the disease made way, and in 1760 it had 

 extended to the Creole population. 



*' Whites of European origin have as yet escaped. 



VOL. IV, N 



