Page:The New International Encyclopædia 1st ed. v. 16.djvu/903

* REGENERATION. 799 REGENERATION. of corresponding size. If, however, the worm be graft, such as the muscles of the legs with those cut longitudinally into a larger and smaller strip, of the stock. -Tandem' unions were more suc- the tormer replaces as much as was contained cessful, a pupa deprived of the head and part of in the smaller part removed, but the smaller the thorax being joined to another deprived of its part does not develop the lost larger part, but abdomen back of the fourth segment. The moths forms only as much new tissue at its cut side as thus resulting had a long body with two sets of IS about equivalent to its own breadth. wings and legs, yet there was "no internal fusion AxiMAL Geaftixg. Although this subject is of organs, only the skin and appendages and not one of practical importance as regards ani Dials, it is a matter of interest connected 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 he 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 Tubularia, Hy- draetinia, 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 HEGENERATIOX OF WORMS. 1. Union of two pieces of AVobopbom terrestris in normal position 22 months after operation. 2. Piece of Lumbncus Tubellus grafted on side of body of another individual to produce a double-tailed worm. 3. Union of two worms (b.v anterior ends) from eacli of which eiglit anterior seg- ments had been removed, (.fter Morgan.) different species, and even of different genera (Lumhricus ruhellus and AUobophoni terrestris), though it was a more difficult undertaking : hut the new worm "reacted as a single individual, and lived for eisht months." As to more special- ized animals, as insects and vertebrates, it ap- pears that as in Crampton's experiments with grafting the pup* of silkmoths (Philosamta Cyn- thia, 8amia 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 pups', / fti- losamia Cynthia upon Samia Cecropia, Callosamta Promethea upon .S'amm Cecropia, but the fusion was entirely a superficial one, there being no in- ternal connection i-"*""-" the orLmns of the wings sharing in the fusion. 'Twin' unions were produced by aboral and oral poles, also lateral 'twin' unions; these experiments were easily per- formed because only a little of each component was cut away. The grafting of tadpoles by Born (1890-97) 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 cases 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 between the organs of GRAFTING A FROG. A combination in which the anterior part of liana esculenta was united to the poeteriorpart of Hnaa tarralie. The blood of the posterior component was driven through the vessels by tlie action of the heart of the anterior com- ponent. The animal lived for 17 days. (Aft«r Morgan.) stock. He succeeded in uniting tadpoles of dif- ferent species in several dilTcrent 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 cases 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 tadjioles even of different genera. It should be observed that in all these and other combinations each developing part retaimi its specific characters, "and although in several cases one part received its nourishment from the other through the common circulation, yet no influence of one component tm the other could be observed." Morgan states that in the mam- mals it is impossible to carry out grafting ex- periments on the same scale as those described in lower forms. Thus we could not graft an arm of a man upon another. While the tissue might have the power to unite, the difficulty would be in supplying the grafted arm with muirishment, etc duriii" the long time required for the union to take piiice. Yet smaller parts of the body mav be succcssfullv grafted, and there are. he savs several recorde.l instances in which parts of"a tinner, or of the nose, are said to have been cut off and to have reunited after being quickly nut back in place. As regards cases of grafting. Hunter and also Duhamel grafted the spur of a ^oiin" cock upon the comb, where it continued to