36 HEREDITY 



digestion and red nose. The real question is whether 

 there is an intimate connection between the various 

 parts of the body and the germ plasm ; whether a 

 change produced by an outside agency on any par- 

 ticular organ comes to be specifically represented in 

 the germ plasm. 



We must now proceed to consider the arguments for 

 and against the inheritance of acquired characters. 



In the first place, it is necessary to note that no one 

 is of the belief that acquired characters are always 

 inherited ; nothing is more easily proved than that 

 the majority are not. If all acquired characters were 

 inherited, even to a very limited extent, our fox-terriers 

 and hackney horses would have become short-tailed, 

 the foot of the Chinese lady would remain small without 

 artificial devices to keep it so, and children in civilised 

 countries would develop ability to read, write, and 

 speak without any education whatever. Nothing 

 would be easier than to accumulate instances of the 

 non-inheritance of modifications. But all negative evi- 

 dence must go for nothing if even a few cases to the 

 contrary can be proved. Let us examine some of the 

 positive evidence, and see whether or not it can be 

 regarded as indisputable proof. 



Numerous instances have been given of the apparent 

 inheritance of mutilations and the like. A case is 

 quoted of a cow which lost one of its horns by ulcera- 

 tion : it had afterwards three calves which showed, 

 " on the same side of the head, no true horn, but a small 

 nucleus of bone hanging to the skin." 



Professor Haeckel quotes a case of a bull having had 

 its tail caught by the slamming of a byre door and 

 squeezed off. The bull subsequently produced tailless 

 calves. 



By far the most important evidence for the in- 

 heritance of the effects of mutilations is furnished by 

 the experiments of Dr. Brown-Sequard on guinea-pigs. 

 In these experiments operations were performed on 

 the spinal cord and nerves of many individuals. In 

 certain cases these operations were followed by a 



