DEVELOPMENT OF DIAPHRAGMA OF XENOPUS LAEVIS IN SIGHT OF COMPARATIVE MYOLOGY

Abstract

At the standpoint of comparative anatomy of the skeletal muscles it is generally accepted that the diaphragma of mammals belongs to the rectus-system, but in the other hand it is pointed out that dia phragma consists of two parts, namely pars ventralis and pars dorsalis; the former belongs to the rectus-system and the letter to the transversus-system, and in man the ventral part is comparable to the pars sterno-costalis and the dorsal part to the pars lumbalis. This dualistic viewpoint comes from the fact that the diaphragma of xenopus laevis possesses both dorsal and ventral parts which are perfectly separated each other; thus xennpus diaphragma is regarded as primitive from.From this sight the author investigated the development of the diaphragma of the xenopus during metamorphosis by dissection under a stereoscoqic binocular microscope and by tinctorial examination on the serial sections. Summarized results are as follows : The ventral part developes from the cells between the larval muscle fibers of the abdominal rectus muscule during stages 56-66 (Nieukoop and Faber). The dorsal part is derived from cell group at the medial side of the anlage of the upper extremity (stage 50) These cells separate from the anlage of upper extremity at the earlier stage.From these observations the author regard the ventral part of the diaphragma as rectus-system and the dorsal part as extremity-muscle.