ANIMAL GRAFTING. Although this subject is not one of practical importance as regards ani mals, it is a matter of interest eonnected with the regeneration of the grafted parts, and in the case of the lower animals may lead, if portions of different species or genera are grafted upon each other, to results bearing on heredity. The first experiments in animal grafting are the famous experiments with the hydras by Trembley. He found that if a hydra is cut in two, the pieces can be reunited by their cut surfaces. the result being a complete animal. He also successfully united the head end of one hydra with the pos terior half of another: but lie failed to obtain a permanent union between individuals of dif ferent species. Lately Wetzel has cut two hydras in two and found that the two anterior pieces united by the aboral cut surfaces, so that each end bore a head with tentacles; he succeeded in a variety of similar experiments. King and others in the same way produced double-headed hydras, and wrought a number of variations on this theme. Lateral grafts were found to differ from lateral buds, the latter after four or five days separating by constricting at the base. Peebles succeeded in grafting in Tuhularia, Hy dra& inia, etc. Joest has succeeded in grafting earthworms, producing double-headed and double tailed specimens. also in splicing, making a long worm out of three separate pieces: he grafted or spliced together with such success worms of different species. and even of different genera (Lumbricus rubcflus and Allobophora terrcstris), though it was a more difficult undertaking: but the new worm "reacted as a .single individual, and lived for eight months." as to more special ized animals, as insects and vertebrates, it ap pears that as in Crampton's experiments with grafting the pnp:r of silkmoths (Phifosomia Cyn thia, Sarnia Cecropia, etc.), like tissues of two components fuse with like, while unlike tissues become organically united by connective tissues. He grafted small pieces upon entire pupa.. Phi losamia Cynthia upon ,antic Cempia, C'u11usan[ia Promethea upon i;amia Cerropia, but the fusion was entirely a superficial one. there being no in ternal connection between the organs of the graft, such as the muscles of the legs with those of the stock. 'Tandem' union, were more suc cessful, a pupa deprived of the head and part of the thorax being joined to another deprived of its abdomen bark of the bairth segment. The moths thus resulting had a long body with two sets of wings and legs, yet there was no internal fusion of oil.-fans, only the skin and appendage, and wings sharing in the fusion. 'Twin' unions were produced by aboral and oral poles, al-o lateral 'twin' unions; these experiments were easily per formed la-cause only a little of each component was cut away.
The grafting of tadpoles by Born ( Is9(-97) has excited much interest. If the anterior half of one tadpole was fused with the hinder half of the same or another tadpole, a single individual was formed which was kept alive in several eases until the time of metamorphosis. If the head of a tadpole is cut off and grafted upon the side of the body of another tadpole, the head will re main alive and continue to develop in its new position, and may grow to the size of that of the stock. He succeeded in uniting tadpoles of dif
ferent species in several different ways. i.e. by their heads, or by their ventral surfaces. or longer and shorter tadpoles were made by using pieces longer or shorter than a half. In all these eases there was no regeneration (says Morgan) at the place of union, and the internal organs, the digestive tract, nervous system. and blood vessels unite when brought into contact. When like organs are brought together the substance of one unites directly with the substance of the other, and if the organ is a hollow one. as is the digestive tract or the nerve-cord. their cavities also become continuous, Born succeeded in grafting tadpoles even of different genera. It should be observed that in all these and other combinations each developing part retains its specific characters, "and although iii several cases one part reveived its nourishment from the other through the common circulation, yet no influence of 011e component on the other could he observed.'' _Morgan states that in the mam mals it is impissible to carry out grafting ex periments 011 t he ,::11111e scale as those des, gibed in tower forms. Thus We could not graft an arm of a man upon another. \\idle the tissue might have the power to unite, the difficulty be in supplying the grafted arm with nourish mt. etc.. during the long time required for the union to take place. Vet smaller parts of the body may be suecessfully grafted. and there aro, he says. several recorded in which parts of a tinger, or of the nose. air- said to have cut Oil :Ind to have reunited after being quickly it back in place. As regards cases of grafting. Hunter and also Dullamel grafted the spur of a young cock upon the comb, where it continued to grow to its normal size. Other similar experi ments have met with varying success.
TRAAsPLANTATION OF SKIN. Cases of this sort of plastic surgery are becoming frequent. Morgan states that pieces of human skin may be without great difficulty grafted upon an exposed surface, •'and it has been said that small pieces succeed better than large ones, owing, most probably, to their being able to absorb sufficient oxygen, etc., and keep alive until new blood-vessels have grown into the grafted piece." The skin of the negro has been transplanted upon a white man. In many cases the transplanted skin has remained alive for a time, yet later it was thrown off by new skin growing under it and replacing it. Even grafting of internal organs is now attempted with more o• less success in operative surgery. The results of grafting bone, etc., adds 'Morgan, that all kinds of tissue may continue to live, and the cells multiply in different parts of the body, but there seems to be nothing in these cases com parable to a regeneration of the entire organ. In the new situation the cells often assume an en tirely new' arrangement. After a period of activ ity. a process of degeneration commences and the piece atrophies.
litntioGnAPIIY. Morgan, Regeneration (New York, 1901 ) , contains a full bibliography; Crampton, "An Experimental Study upon Lepi doptera." in Arehir file Ent wiefrelungsmechanik der Organismen, vol. ix. (1899).