“‘6th. Hæmatoma and dry gangrene of the ears in animals born of parents in which these ear-alterations had been caused by an injury to the restiform body near the nib of the calamus.
“‘7th. Absence of two toes out of the three of the hind leg, and sometimes of the three, in animals whose parents had eaten up their hind-leg toes which had become anæsthetic from a section of the sciatic nerve alone, or of that nerve and also of the crural. Sometimes, instead of complete absence of the toes, only a part of one or two or three was missing in the young, although in the parent not only the toes but the whole foot was absent (partly eaten off, partly destroyed by inflammation, ulceration, or gangrene).
“‘8th. Appearance of various morbid states of the skin and hair of the neck and face in animals born of parents having had similar alterations in the same parts, as effects of an injury to the sciatic nerve.’
“It should be especially observed that Brown-Séquard has bred during thirty years many thousand guinea-pigs from animals which had not been operated upon, and not one of these manifested the epileptic tendency. Nor has he ever seen a guinea-pig born without toes, which was not the offspring of parents which had gnawed off their own toes owing to the sciatic nerve having been divided. Of this latter fact thirteen instances were carefully recorded, and a greater number were seen; yet Brown-Séquard speaks of such cases as one of the rarer forms of inheritance. It is a still more interesting fact, ‘that the sciatic nerve in the congenitally toeless animal has inherited the power of passing through all the different morbid states which have occurred in one of its parents from the time of the division till after its reunion with the peripheric end. It is not, therefore, simply the power of performing an action which is inherited, but the power of performing a whole series of actions, in a certain order.’
“In most of the cases of inheritance recorded by Brown-Séquard only one of the two parents had been operated upon and was affected. He concludes by expressing his belief that ‘what is transmitted is the morbid state of the nervous system,’ due to the operation performed on the parents.”
Mr. Darwin proceeds to give other instances of inherited effects of mutilations:—
“With the horse there seems hardly a doubt that exostoses on the legs, caused by too much travelling on hard roads, are inherited. Blumenbach records the case of a man who had his little finger on the right hand almost cut off, and which in consequence grew crooked, and his sons had the same finger on the same hand similarly crooked. A soldier, fifteen years before his marriage, lost his left eye from purulent ophthalmia, and his two sons were microphthalmic on the same side.”
The late Professor Rolleston, whose competence as an observer no one is likely to dispute, gave Mr. Darwin two cases as having fallen under his own notice, one of a man whose knee had been severely wounded, and whose child was born with the same spot marked or scarred, and the other of one who was severely cut upon the cheek, and whose child was born scarred in the same place. Mr. Darwin’s conclusion was that “the effects of injuries, especially when followed by disease, or perhaps exclusively when thus followed, are occasionally inherited.”
Let us now see what Professor Weismann has to say against this. He writes:—
“The only cases worthy of discussion are the well-known experiments upon guinea-pigs conducted by the French physiologist, Brown-Séquard. But the explanation of his results is, in my opinion, open to discussion. In these cases we have to do with the apparent transmission of artificially produced malformations . . . All these effects were said to be transmitted to descendants as far as the fifth or sixth generation.