HEREDITY. 251 



be assumed between constitutional consumption and con- 

 sumption induced by unwholesome conditions — unless it be 

 asserted that consumption of unknown origin is transmiss- 

 ible, while functionally-produced consumption is not ; it 

 must be admitted that those changes of structure from which 

 the consumptive diathesis results, may be caused in parents 

 by changes of function, and may be inherited by their chil- 

 dren. Most striking of all, however, is the fact lately 

 brought to light, that functional disorders artificially estab- 

 lished, may be conveyed to offspring. Some few years since 

 M. Brown-Sequard, in the course of inquiries into the nature 

 and causes of epilepsy, hit on a method by which epilepsy 

 could be originated. . Guinea-pigs were the creatures on 

 which, chiefly, he experimented ; and eventually, he disco- 

 vered the remarkable fact, that the young of these epileptic 

 guinea-pigs were epileptic : the functionally-established 

 epilepsy in the parents, became constitutional epilepsy in. the 

 offspring. Here we have an instance which, standing even 

 alone, decides the question. We have a special form of nervous 

 action, not caused by any natural variation of structure that 

 had arisen spontaneously in the organism, but one caused 

 by a certain incidence of external forces. We have this 

 special form of nervous action becoming confirmed by re- 

 petition : the fits are more and more easily induced — there is 

 established the epileptic habit. That is to say, the connected 

 nervous actions constituting a fit, produce in the nervous 

 system such changes of structure, that subsequent connected 

 nervous actions of like kind, follow one another with increased 

 readiness. And that this epileptic habit is inherited, proves 

 conclusively that these structural modifications worked by 

 functional modifications, are impressed on the whole organism 

 in such way as to affect the reproductive centres, and cause 

 them to unfold into organisms that exhibit like modifications. 

 Evidence nearly allied to this, and scarcely less significant, 

 is furnished by that transmission of general nervousness, no- 

 ticed in the last section. Nervousness is especially common 



