J. Playfair McMurrich 35 



muscle mass whose fibres have a markedly oblique direction and which 

 will be spoken of as the plantaris profundus III (Pp^^^). Beneath the 

 fibular border of this there is a small oval muscle whose fibers are cut 

 transversely and which is the fihulo-tarsalis (FT), Avhile opposite its 

 tibial border there is a very slender muscle which may be termed the 

 plantaris p-o fundus III minor (Pp^^^m). Still more deeply seated 

 are two layers of muscle whose fibers are directed obliquely downward 

 and tibia-wards, the plantares profundi II and I (Pp^^ and Pp^), and 

 finally, extending almost directly across between the fibula and tibia is 

 a muscular slieet which may be termed the m. interosseus (I). 



A comparison of such a section with one taken through the forearm 

 of Amblystoma will show that a remarkable similarity exists between 

 the two. There is exactly the same number of layers and the same 

 direction of the fibers in the different layers. Indeed, the resemblance 

 is so close that the two sections might easily be confused in a casual 

 examination. A discussion of their resemblances and the significance 

 of these will, however, be postponed until a later occasion, and I shall 

 pass on now to a consideration of the various muscles mentioned above. 



And first as to the plantaris superficially medialis (Psm). As already 

 noted, this muscle is not regarded by Eisler as a part of the crural mus- 

 culature and in this view he is in agreement with his predecessors. The 

 muscle is continuous above with the lower end of the muscle named 

 ischio-fiexorius by Hoffmann, 73, the caudo-pedal by Humphry, 72, and 

 the external flexor of the crus by Perrin, 93, and, indeed, is tlie terminal 

 part of that muscle. Prom dissections there is little reason to regard 

 it otherwise than as these authors have done, but its relations as seen in 

 sections, especially when these are compared with sections through the 

 forearm, speak so strongly for the view here set forth that I have no 

 hesitation in advancing it. And especially so since there are two other 

 facts bearing favorably upon it, namely (1) the insertion of the muscle 

 into the plantar aponeurosis, which occurs a short distance below the 

 knee joint, and (2) the fact that in Amblystoma the ischio-flexorius 

 is crossed at the knee joint by a well-marked tendinous inscription, which 

 marks, I believe, the line of junction of the ischio-flexorius proper with 

 the plantaris superficialis medialis. The ischio-flexorius of Hoffmann 

 is, according to this view, a compound muscle formed by the end to end 

 union of a true ischio-flexorius with a plantaris superficialis medialis.* 



= If I understand aright Humphry's, 72, description of the caudo-pedal 

 muscle of Cryptobranchus, there is in this form also a tendinous inscription 

 in the muscle in the neighborhood of the knee joint. If this be so, it is 



