THE MUSCLES 



Flexores abducentes 



Stannius (1854-6). 



Mivart (1869). 



Humphry (1872). 



Hoffmann (1873-8). 



Perrin (1892). 



Semitendinosus .... 



Caudo-pedalis .... 



Ischio-flexorius (Semimembranosus) . 



Flechisseur externe de la jambe (115) 

 Proximal portion = 



Ischio-flexorius ...... McMurrich (1904). 



Distal portion = 



Plantaris superficialis medialis .... McMurrich (1904). 



A Strap-like muscle, which arises from the posterior ventro-lateral 

 angle of the os ischium, immediately behind the M. pub. isch. tib. 

 During its course along the ventro-posterior border of the thigh it 

 passes dorsal to the insertion of the M. caud. pub. isch. tib. into the 

 M. pub. isch. tib. At the popliteal region it becomes more mesial 

 and passes to about the middle of the flexor surface of the leg, and, 

 at a point about midway between the knee and the ankle, it dis- 

 appears into a tendon which mingles with the plantar aponeurosis of 

 the M. flexor primordialis communis. 



This muscle had always been regarded as a single muscle until 

 1904, when McMurrich, during his investigation of Amblystoma, 

 noticed that its fibres were interrupted by a tendinous inscription at 

 about the level of the knee, and hence he suggested that the muscle 

 was really composed of two separate muscles fused end to end. The 

 proximal portion he regarded as the true ischio-flexorius, but the 

 distal portion he thought was the serial homologue of the superficial 

 flexor muscle of the fore-arm, which arises from the humerus (M. 

 flex. prim, comm.), and he named it accordingly M. plantaris super- 

 ficialis medialis. McMurrich based his view largely upon the 

 appearance of the cross-section of the leg just below the knee com- 

 pared with that of the fore-arm below the elbow, and on the fact 

 that otherwise a superficial flexor with parallel longitudinal fibres is 

 wanting in the hind-limb {vide infra). 



In Salamandra the relations of the M. ischio-flexorius are very 

 similar to those described by McMurrich for Amblystoma. That 

 two muscles are involved in the composition of this adult 'ischio- 

 flexorius' seems almost certain, since the innervation of the two 

 portions is different. While it may be that McMurrich's inter- 

 pretation is correct it is nevertheless open to doubt, and, until a 

 thorough investigation of the ontogeny of the muscle is available, it 

 seems preferable to retain the name 'ischio-flexorius' for the whole 

 muscle and to apply the term pars propria to the proximal portion, 

 2ind pars plantaris to the distal portion. 



