The appendicular muscles of Necturus maculosus. 411 



margin of which it curves to its extensive insertion on the femur. 

 In following this course the muscle becomes divided into two portions 

 by the ilium, which projects dorsally between its fibers, but these 

 portions become joined again lipon the outer side of the ilium by 

 a bundle of fibers which arise from the lateral aspect of the ilium 

 itself, and the three become absolutely continuous long - before the 

 insertion is reached. The muscle is thus extremely difficult to demon- 

 strate and needs for its complete exposition views from several 

 different aspects, the most of which demand special dissection and 

 the sacrifice of many of the adjacent structures. Thus the part 

 which is visible lipon the outer side of the leg- when the latter is 

 in its more usual position (Figs. 11, 12) is merely the distal portion, 

 and the manner of its insertion can be realised only by elevating 

 the femur of a specimen from which the ventral muscles have been 

 cleared (Fig. 13). 



To study this muscle to advantage it is necessary first to remove 

 from the body the entire puboischiadic plate with the legs attached, 

 cutting through the ilia, and then to cut away entirety the iliac 

 muscles of one side, especially Mm. iliotibialis, ilioextensorius, and 

 iliofemerofibularis. The femur should be extended laterally and the 

 projecting ilium should be cut off to about the level of the muscle. 



Yiewing this preparation now from the dorsal side the muscle 

 in question is revealed throughout nearly its entire extent, and 

 appears as a vast sheet, streched between the puboischium and the 

 femur, its fibers flowing - completely around the truncated ilium and 

 reuniting- upon the other side (Fig. 14). Although anatomically the 

 muscle is not easily separated into distinct portions it is convenient 

 for purposes of description to divide it into three heads, anterior, 

 middle, and posterior. The anterior portion arises from along the 

 median line of the dorsal surface of the puboischium, extending 

 from the anterior end of the epipubic process to the puboischiadic 

 fossa. At its origin the muscle is in the form of a thin lamella, 

 but receives from beneath additional fibers from the anterior side 

 of the ridge that bounds the puboischiadic fossa anteriorly, after 

 which the muscle becomes thicker and blends with the other portions. 

 The posterior portion arises from the side and bottom of the pubo- 

 ischiadic fossa, its most anterior fibers approaching - so nearly to 

 the most posterior ones of the anterior portion that the two are 

 separated only by the ridge that bounds the fossa anteriorly. The 

 lateral or external portion arises from the outer surface of the 



