George Johnson
1875 The Lancet  
8 the change in shape of the ear. The absence of toes is rare. Since I have paid attention to it as an instance of hereditary transmission I have only recorded it thirteen times, although I know that I have seen it in more than thirteen animals. I have come to the conclusion that this condition of the foot deprived of toes is due to heredity from this reason, that I have never seen a guinea-pig born toeless which was not the offspring of parents accidentally deprived of toes. Besides, the
more » ... ital absence of toes has never existed but in the hind legs, limbs which were also the only toeless ones in the parents. I should say, however, that in two animals both hind legs were partly toeless, while the father in one case, and the mother in the other, had toes missing only in one of the hind legs. A similar observation I have made, and already mentioned, as regards the protrusion of the eyeballs ; a number of animals had both eyes protruding, although their parents had exophthalmia onlv on one side. ill IIIUSU ur Liit? iu6uEtLi-ces VL uertJulI,y tuau L ll0.VC USt;lVU only one of the parents had been operated upon, and had the alteration which was transmitted. I now come to the fact to which I wish especially to call attention. I have made the following observations only in two animals, but in both of them all the features I will mention were perfectly manifest. I have already stated that the young of guinea-pigs born of parents having had a section of the sciatic nerve sometimes become epileptic. This inherited epilepsy I have never observed in other animals than those which had also inherited an absence of toes. Now, as regards these toeless animals, I have been able in two of them, as already "t!lt,øtl 1n fnllnm nn ihn ilinviffoq T vi7i]l n,ønt,l"n I It is pretty well known that I have found that some time after the section of the sciatic nerve in guinea-pigs the sensibility of the skin of some parts of the face and neck on the side of the operation becomes very different from what it was; it diminishes as regards its power of giving rise to pain under a prick, a pinch, or a galvanic current, at the same time that appears in that skin the power, when tickled or gently pinched, to produce some convulsive reflex movement. At first there is only a reflex spasm of some muscles of the face and neck; gradually the number of muscles contracting and the energy of the spasm increase, and after a few days the whole side of the body on which the nerve has been divided contracts powerfully. A little later the muscles of the other side become also convulsed, and the head is shaken to and fro from side to side. A few days later the attack becomes more complete. Not only the convulsions are more easily produced and become more violent, but also there is sometimes loss of consciousness and a state of torpor, stupidity, and even in a few instances of insanity, for a while after the attack. In the meanwhile the divided ends of the sciatic nerve begin to unite, and when reunion progresses, three very remarkable facts can be witnessed. The skin of the face and neck recover gradually their sensibility to mechanical or galvanic irritation, the fits gradually diminish in intensity, the changes for the better occurring just by opposite steps to those followed while the trouble was increasing, and we find also that the hair gradually falls off from the cutaneous zone, the excitation of which by tickling or gentle pinching was able to give rise to an epileptic attack. The beginning of this fall of hair marks the turning-point of the nervous affection. As soon as it appears, a decrease of violence of the convulsive complaint begins to be noticed. Now all these peculiarities-the gradual increase of the affection, the diminution of sensibility in the epileptogenotts zone, the coming of a period of complete attacks of epilepsy, and then the loss of hair, and the gradual diminution of the nervous complaint-all these things in all their details I have witnessed also in two guinea-pigs born toeless by hereditv. and having also bv hereditv become epileptic. There is therefore an inheritance not only of an aptitude of being seized with convulsions, but of the whole nervous affection of the father or mother in all its features, from beginning to end, and in the same order. This certainly is quite remarkable, but what is still more so is that in the parent there are changes which we know to occur in the sciatic nerve, which we find to be connected with the different stages of the convulsive affection, and especially there is the co-existence of the reunion of the divided nerve and of the amelioration at the time of the fall of hair; while in the toeless-born animals there is no division of the sciatic nerve to give rise to the trouble, and still less a reunion of separated ends of nerve to explain the amelioration. We must conclude therefore 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 in the central end of thesciatic nerve 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 the whole of a series of actions, and in a certain order. In almost all, if not in all, the cases of hereditary transmission I have observed in animals in whose parents I had injured either the sciatic nerve, the cervical sympatheticnerve, or the corpus restiformis, most likely what is transmitted is the morbid state of the nervous system. There ispossibly an exception in the fact that some animals wer& born toeless from their parents having lost their toes; but the other facts only imply the transmission of a morbid state of the sympathetic or sciatic nerve or of a part of the medulla oblongata. These facts, added to many others mentioned bv P. Lucas* and by Charles Darwin, clearly prove the possibility of hereditary transmission of effects of mere accidental injuries. ON CERTAIN POINTS RELATING TO THE
doi:10.1016/s0140-6736(02)30915-2 fatcat:xiybnajvqzemxe3f4yy7ymg6sm