80 J. A. BADERTSCHER 



that they are extrinsic in their nature and is of the opinion that a 

 lack of nutrition or atrophy through disuse after the appearance 

 of the forelegs, are factors to be considered. 



According to Katz ('00), who worked with transforming toads, 

 the initiatory causes of degeneration appear to be intrinsic in the 

 muscle itself. Sarcolytes are formed only in some fibers. In the 

 course of degeneration a homogeneous material is produced, which 

 disappears by liquefaction in situ. 



Looss ('92) arrived at practically the same conclusions as those 

 of Barfurth, with the exception that a small portion (less than 10 

 per cent) of the sarcolytes are taken up and destroyed by the pha- 

 gocytes. The remaining large proportion undergo dissolution in 

 place through the activity of the surrounding fluids. 



Metchnikoff ('84), in his work on larval frogs, held that muscle 

 degeneration was effected entirely through the action of phago- 

 cytes which collected in large numbers among the degenerating 

 fibers. The source of the numerous phagocytes he then ascribed 

 to the blood. Further investigations ('92) led him to modify the 

 phagocytosis theory of muscle degeneration. In his later work he 

 holds that the phagocytes, which play the important part in muscle 

 degeneration, are formed in the muscle fiber. The first percep- 

 tible changes in degeneration are a proliferation of muscle nuclei 

 and an increase in the amount of sarcoplasm. The muscle nuclei 

 and protoplasm then differentiate into cells, the muscle phago- 

 cytes, which find their way among the fibrillae, breaking them up 

 into fragments. These fragments (sarcolytes) are ingested and 

 removed by them. The usual type of phagocytes takes no part 

 in muscle degneration, that work being entirely limited to the 

 muscle phagocytes. 



Muscle degeneration in Salamandra atra is, to all appearances, 

 a purely aphagocytic process. However, on comparing the degen- 

 erating jaw muscles in this class of animals with those in the 

 tails of larval toads, a marked point of difference is recognized in 

 that the formation of sarcolytes does not occur in the former. 

 On examining a series of toads from the larval to the adult condi- 

 tion, sarcolytes in the degenerating tail muscles were found as 

 described by the investigators mentioned above. In the Sala- 



