686 



Regeneration 



generate of the male type. A masculinized 

 female has a declining regenerative capacity 

 from which it does not recover after the 

 withdrawal of androgen. 



In Gambusia, Turner ('47) has given the 

 results on normal and castrated males. In 

 the castrate the rate of regeneration is the 

 same as for juvenile males or females. Hop- 

 per ('49a) has performed the same experi- 

 ments on both males and females of Lebistes 

 where the castrate females regenerate nor- 

 mally while the castrate males regenerate a 

 female type of fin. When he exposed the 

 fishes to ethynyl testosterone in two con- 

 centrations (Hopper, '49b) the females de- 

 veloped and also could regenerate typical 

 anal fins; the males showed no loss of re- 

 generative capacity. These three investiga- 



Fig. 242. Vertebral breaking point in the lizard tail 

 {Lacerta muralis) (from Slotopolsky, '21-'22). 



tors, using similar methods for the study of 

 three different teleost fishes, show how very 

 different the regenerative behavior can be 

 in respect to hormonal activity. 



In the uz^odeles, Schotte and Hall ('52) 

 have tested the effects of hypophysectomies 

 performed at varying times on the formation 

 of the regenerating forelimb. The wound- 

 healing phase was severely affected by the 

 hormonal imbalance, dedifferentiation was 

 affected but not so severely, while blastema 

 and growth phases were hardly affected at 

 all. They propose that the growth factor is 

 not the acting one, but that probably it is 

 the ACTH factor acting through cortisone 

 to regulate the wound epidermis action upon 

 the cut stump tissvies. Considerably more in- 

 formation will be needed before this mecha- 

 nism of action can be confirmed. 



Richardson ('45) has studied the effect of 

 the interrelationship of the thyroid and 

 hypophysis upon hind limb regeneration. 

 The hypophysis in the absense of the thyroid 

 has a greater inhibiting effect than thyroid 

 acting alone in the absence of the hypophy- 

 sis. When Antuitrin-G and thyroxine were 

 supplied as substitutes for the hypophysis 

 and thyroid, respectively, good cartilaginous 

 skeletal regeneration was secured. Regenera- 

 tion without removal of hypophysis and 

 thyroid is accelerated by Antuitrin-G. 



REPTILIAN REGENERATION 



Fraisse (1885) listed thirty or forty cases 

 of regeneration observed chiefly on lizards, 

 with a few observations on the serpents. 

 There are also a few scattered observations 

 upon some of the turtles. The double- and 

 triple-tailed lizards, however, held most of 

 the attention, but in the category of abnor- 

 mality rather than regeneration. These are 

 naturally occurring forms. 



Cuvier (1829) commented on the neces- 

 sity for the study of regeneration in the 

 lizard and remarked concerning his interest 

 in the abnormal development of bone after 

 autotomy. Gachet (1833) found that regen- 

 eration was not confined to the lizards 

 Lacerta agilis and L. viridis, but that it was 

 possessed in varying degrees in others of 

 the reptiles. He examined five lizards with 

 double tails, four with regenerating tails 

 and several with single or double regen- 

 erating tails. Of the native forms, L. muralis, 

 L. viridis and L. ocellata were represented, 

 and also Anolis iguana. His findings were 

 all verified by dissections and are com- 

 pletely described in Fraisse's (1885) mono- 

 graph. Gachet gives the literature to his 

 date, together with a description of cases 

 under discussion. 



Guyenot and Matthey ('28) and Guyenot 

 and Ponse ('30) traced the regeneration of 

 the limb and repeated Fraisse's work on the 

 formation of the blastema and the regenera- 

 tion of the tail. Weiss ('23) tested the effect 

 of transplantation on the regenerate as well 

 as the effect of the whole upon the graft 

 and the graft upon the whole. A tail blas- 

 tema transplanted to the limb region regen- 

 erates a miniature tail, not a limb. Occasion- 

 ally when a small strip of tissue or a small 

 incision is made near the hind limb, a 

 small but imperfect tail results. 



Slotopolsky ('21-22) restudied the mech- 

 anism of autotomy in the lizard Lacerta 

 and found the explanation of the evenness 

 of level with which it occurs, for there are 

 two vertebrae behind the pelvic girdle in 

 which the midpoint of the vertebra is an 

 unfused part, giving a rough articular sur- 

 face which, because of strong muscular con- 

 traction, serves as a line of cleavage. While 

 other forms of autotomy occur in the higher 

 vertebrates, this is the only series recorded 

 in which the mechanism is similar to the 

 much more efficient mechanism of the ar- 

 thropods. Many rodents autotomize the tail 

 but the epidermis is all that is lost. Sumner 

 and Collins ('18) described this process for 

 Peromyscus. Other forms tend to chew parts 



