286 SCIENCE PROGRESS. 



generations, a sort of habit may be acquired, by which the 

 new state becomes as it were natural, and may thus modify 

 the race ". To this he rephes that the evidence of such 

 habit could only be obtained by diminishing the mutilation 

 in progressive generations and comparing the result; whereas 

 in all such cases the violence committed and the resulting 

 injuries are continued unabated. " If, however, an experi- 

 ment be wanting to prove that repetition effects no difference 

 in the results," he points to the practice of circumcision 

 which has gone on for some thousands of years without 

 producing any hereditary change. 



Prichard argues that such non-tranmission is beneficial, 

 in fact he contends "that all the laws of nature, or the 

 general plans which we trace through the organized 

 world, tend uniformly to produce beneficial effects, though 

 particular' evils are sometimes contingent upon their opera- 

 tion". With regard to this instance he points out that, if such 

 transmission took place, both man and animals would prac- 

 tically become more and more " mutilated and defective". 



The author next proceeds to consider the effects of 

 disease, introducing the subject in the following paragraph : 

 " we cannot discern any essential circumstance in which 

 changes produced by art or by casual injury differ from 

 those which are effected by other external causes. We 

 should therefore suppose from analogy that the latter are 

 not more communicable to posterity than the former, and 

 this presumption is confirmed when we inquire into facts," 



He points out that the constitutional effects of many 

 diseases ("small-pox, measles, scarlatina, whooping-cough"), 

 rendering those who have suffered from them more or less 

 immune, are never hereditary. Without attempting to 

 explain in what the change consists, he rightly claims it as 

 "a permanent state of the constitution, which lasts as long 

 as the individual. . . . Those imperceptible modifications in 

 the bodily structure which render the constitution incapable 

 of being acted upon by certain morbid poisons are governed 

 by the same law, as far as regards hereditary descent, as 

 the observable changes of form which are induced by art or 

 accident." 



