TRANSMISSION OF MODIFICATIONS 369 



disease or whether it is caused by weakness in family lines des- 

 tined to disappear, and for whose extinction tuberculosis is the 

 special agent of natural selection. The weight of evidence inclines 

 the writer to a belief in progressive immunity from diseases of this 

 class, a matter touched upon under the subject of acclimati- 

 zation. That the spavined mare will not transmit her spavin is 

 as fortunate as it is true, but the question lying back of this 

 fact is, Why was she spavined ? Is the injury an evidence of 

 weakness, or is it only the result of an accident, such as might 

 have happened to any horse ? If it is the former, then the 

 weakness, not the spavin, will be transmitted ; if it is the latter, 

 there is in all probability not the slightest danger. If injuries of 

 this sort were transmissible, our horses would long since have 

 acquired a collection of spavins, ringbones, splints, sidebones, 

 and curbs such that no leg could hold them. It is far from the 

 purpose of the writer to advocate the use of defectives as 

 breeders, but we cannot close our eyes to the fact that a mare 

 which has seen hard service and bears the marks of it is in all 

 likelihood a better breeder than another that has never been put 

 to the test, no matter how clean and free from blemishes the 

 limbs of the latter may be. The stubborn fact is that the risk 

 of accident is so great that a horse put to hard service is certain 

 to be blemished sometime ; and so far as present knowledge goes, 

 she is as good a breeder after the accident as she was before, 

 which is far from saying that every blemished horse is fit for 

 breeding purposes. 



The writer is clearly of the opinion that, even with the ex- 

 periments of Brown-Sequard in mind, the evidence warrants 

 the conclusion that ordinary injuries to the body are not trans- 

 mitted to the offspring. Whether different results follow those 

 profound injuries that reach the nerve centers and work con- 

 stitutional changes in the organism is a matter on which we 

 must await further evidence. 



Mutilations have reference to characters already fully devel- 

 oped, and therefore fully provided for in the germinal matter. 

 If violent removal is to lead to their suppression, it must lead to 

 it through some sort of retroactive influence affecting the germ 

 in exactly the proper particular and no other, a presumption 



