THE HORSE. 



133 



loss or severe injury of the original mem- 

 bers ; and in the Triton a perfect eye has 

 been formed to replace one which had been 

 removed. In the true Lizards^ an imper- 

 fect reproduction of the tail takes place, 

 when a part of it has been broken off; but 

 the newly-developed portion contains no 

 perfect vertebraB, its centre being occupied 

 by a cartilaginous column, like that of the 

 lowest Fishes. In the warm-blooded Ver- 

 tebrata generally, as in Man, the power of 

 true reproduction after loss or injury seems 

 limited, as Mr. Paget has pointed out,* to 

 three classes of parts, namely : (1.) ' Those 

 which are formed entirely by nutritive rep- 

 etition, like the blood and epethelia, their 

 germs being continually generated de novo 

 in the ordinary condition of the body ; (2.) 

 Those which are of lowest organization, 

 and (which seems of more importance) of 

 lowest chemical character, as the gelatinous 

 tissues, the areolar and tendinous, and the 

 bones; (3.) Those which are inserted in 

 other tissues, not as essential to their struc- 

 ture, but as accessories, as connecting or 

 incorporating them with the other struc- 

 tures of vegetative or animal life, such as 

 nerve-fibres and blood-vessels. With these 

 exceptions, injuries or losses are capable of 

 no more than repair, in its more limited 

 sense ; i. e., in the place of what is lost, 

 some lowly organized tissue is formed, 

 which fiUs up the breach, and suffices for 

 the maintenance of a less perfect life.' 

 Yet, restricted as this power is, its opera- 

 tions are frequently most remarkable ; and 

 are in no instance, perhaps, more strikingly 

 displayed, than in the re-formation of a 

 whole bone, when the original one has been 

 destroyed by disease. The new^ bony mat- 

 ter is thrown out, sometimes within, and 

 sometimes around, the dead shaft; and 

 when the latter has been removed, the new 

 structure gradually assumes the regular 

 form, and all the attachments of muscles, 

 ligaments, etc., become as complete as be- 

 fore. A much greater variety and com- 

 plexity of actions are involved in this 



* " Lectures on Reproduction and Repair." 



process, than in the reprocjuction of whole 

 organs in the simpler animals ; though 

 its effects do not appear so striking. It 

 would seem that in some individuals this 

 regenerating power is retained to a greater 

 degree than it is by the class at large ; * and 

 here again we find, that in the early period 

 of development the power is more strongly 

 exerted than in the adult condition. The 

 most remarkable proof of its persistence even 

 in Man, has been collected by Prof. Simp- 

 son; who has brought together numerous 

 cases in which, after ' spontaneous amputa- 

 tion of the limbs of a foetus in utero,' occur- 

 ring at an early period of gestation, there 

 has obviously been an imperfect effort at 

 the re-formation of the amputated part 

 from the stump.f By the knowledge of 

 these facts and principles, we seem justi- 

 fied in the surmise, that the occm-rence 

 of supernumerary or multiple parts is 

 not always due (as usually supposed) to 

 the 'fusion' of two germs, but that it 

 may result from the subdivision of one ; 



* One of the most curious and well-authenticated in- 

 stances of this kind is related by Jlr. White, in his work 

 on tlie " Regeneration of Animal and Vegetable Sub- 

 stances," 1785, p. 16. "Some years ago, I delivered a 

 la'dy of rank of a fine boy, who had two thumbs upon one 

 hand, or rather, a thumb double from the first joint, the 

 otlier one less than the other, each part having a pei-fcct 

 nail. When he was about three years old, I was desired 

 to take oiF the lesser one, which I did ; but to my great 

 astonishment it grew again, and along with it the nail. 

 The family aftei'n'ards went to reside in London, where 

 his father showed it to that excellent operator, William 

 Bromfield, Esq., surgeon to the Queen's household ; who 

 said, he supposed Mr. 'WTiite, being afraid of damaging 

 the joint, had not taken it wholly out, but he would dis- 

 sect it out entirely, and then it would not return. He ac- 

 cordingly executed the plan he had described, with great 

 dexterity, and turned the ball fiiirly out of the socket; 

 not%vithstanding this, it grew again, and a fresh nail was 

 foi-med, and the thumb remained in this state." The 

 Author has been himself assured by a most intelligent 

 Surgeon, that he was cognizant of a case in which 

 the whole of one ramus of the lower jaw had been 

 lost by disease in a young girl, yet the jaw had been com- 

 pletely regenerated, and teeth were developed and occu- 

 pied then- normal situations in it. 



t These cases were brought by Prof. Simpson before 

 the Physiological Section of the British Association, at 

 its meeting in Edinburgh, August, 1850. The Author, 

 having had the opportunity of examining Prof. Simpson's 

 preparations, as well as two living examples, is perfectly 

 satisfied as to the fact. 



