REGROWTH OF AMPUTATED PARTS.
This subject deserves a little further discussion. A multitude of the lower animals and some vertebrates possess this wonderful power. For instance, Spallanzani cut off the legs and tail of the same salamander six times successively, and Bonnet (27/18. Spallanzani 'An Essay on Animal Reproduction' translated by Dr. Maty 1769 page 79. Bonnet 'Oeuvres d'Hist. Nat.' tome 5 part 1 4to. edition 1781 pages 343, 350.) did so eight times; and on each occasion the limbs were reproduced on the exact line of amputation, with no part deficient or in excess. An allied animal, the axolotl, had a limb bitten off, which was reproduced in an abnormal condition, but when this was amputated it was replaced by a perfect limb. (27/19. Vulpian as quoted by Prof. Faivre 'La Variabilite des Especes' 1868 page 112.) The new limbs in these cases bud forth, and are developed in the same manner as during the regular development of a young animal. For instance, with the Amblystoma lurida, three toes are first developed, then the fourth, and on the hind-feet the fifth, and so it is with a reproduced limb. (27/20. Dr. P. Hoy 'The American Naturalist' September 1871 page 579.)
The power of regrowth is generally much greater during the youth of an animal or during the earlier stages of its development than during maturity. The larvae or tadpoles of the Batrachians are capable of reproducing lost members, but not so the adults. (27/21. Dr. Gunther in Owen 'Anatomy of Vertebrates' volume 1 1866 page 567. Spallanzani has made similar observations.) Mature insects have no power of regrowth, excepting in one order, whilst the larvae of many kinds have this power. Animals low in the scale are able, as a general rule, to reproduce lost parts far more easily than those which are more highly organised. The myriapods offer a good illustration of this rule; but there are some strange exceptions to it--thus Nemerteans, though lowly organised, are said to exhibit little power of regrowth. With the higher vertebrata, such as birds and mammals, the power is extremely limited. (27/22. A thrush was exhibited before the British Association at Hull in 1853 which had lost its tarsus, and this member, it was asserted, had been thrice reproduced; having been lost, I presume, each time by disease. Sir J. Paget informs me that he feels some doubt about the facts recorded by Sir J. Simpson ('Monthly Journal of Medical Science' Edinburgh 1848 new series volume 2 page 890) of the regrowth of limbs in the womb in the case of man.)
In the case of those animals which may be bisected or chopped into pieces, and of which every fragment will reproduce the whole, the power of regrowth must be diffused throughout the whole body. Nevertheless there seems to be much truth in the view maintained by Prof. Lessona (27/23. 'Atti della Soc. Ital. di Sc. Nat.' volume 11 1869 page 493.), that this capacity is generally a localised and special one, serving to replace parts which are eminently liable to be lost in each particular animal. The most striking case in favour of this view, is that the terrestrial salamander, according to Lessona, cannot reproduce lost parts, whilst another species of the same genus, the aquatic salamander, has extraordinary powers of regrowth, as we have just seen; and this animal is eminently liable to have its limbs, tail, eyes and jaws bitten off by other tritons. (27/24. Lessona states that this is so in the paper just referred to. See also 'The American Naturalist' September 1871 page 579.) Even with the aquatic salamander the capacity is to a certain extent localised, for when M. Philipeaux (27/25. 'Comptes Rendus' October 1, 1866 and June 1867.) extirpated the entire fore limb together with the scapula, the power of regrowth was completely lost. It is also a remarkable fact, standing in opposition to a very general rule, that the young of the aquatic salamander do not possess the power of repairing their limbs in an equal degree with the adults (27/26. Bonnet 'Oeuvres Hist. Nat.' volume 5 page 294, as quoted by Prof.