MYOLOGY OF THE ORNITHORHYNCHUS . 159 



and ninth dorsal from below, and by digitations from the contiguous 

 portions of ribs, especially a few of the lower ones. Its flattened 

 tendon, dense and glistening, extends upward upon its anterior bor- 

 der. It has definite insertion into the pectihagal eminence. 



X. Muscles of the posterior extremity. 



On reflecting the skin and panniculus, the whole limb down nearly 

 to the heel, is seen to be enwrapped in three large, broad muscles ; on 

 the outside lie the enormous ectogluteeus and the remarkably ex- 

 panded biceps ; on the other side lies the great gracilis, second only 

 to the gluteus itself in size and strength. 



a. Acting upon the femur. 



Perhaps the most notable peculiarity is the absence of gluteus max- 

 imus from this group, this muscle's insertion being carried down to the 

 leg below. .Psoas magnus and iliacus are much blended, and have re- 

 markably extensive fleshy insertion ; the same may be said of the two 

 smaller glutoei. We can find no trace of scansorius nor of tensor fas- 

 cice latce. There are three perfectly distinct adductores femoris besides 

 the pectinceiis, making a fourth. Pyriformis is present ; so are quad- 

 ratus femoris, and the two obturatores, though the latter has no origin 

 v-ithin the pelvis (being shut off by the ischio-coccygeal muscle) and 

 does not develop gemelU. There is another little ischio-femoral mus- 

 cle that we do not identify. Further details will be found under spec- 

 ial heads of the muscles ; but we may add here, that the femur, like 

 the humerus, is extremely short, thick, strong, and irregular in super- 

 ficies, contributing by its shape to forcible, rather than extensive, 

 movements of the limb. It has scarcely a "neck;" its large head 

 is embedded between two expanded trochanters of nearly equal size, 

 projecting like ears or wings on opposite sides ; below these the bone 

 rapidly narrows to expand again into large condyles, whereof the 

 outer is especially developed for extensive fibular connections. It is 

 curious to find that there is no noticeable gx'oove between the con- 

 dyles in fi-ont, although there is a very large and well-formed patella ; 

 this is contrary to the general proposition, that depth of groove 

 and size of patella are reciprocal or complementary, if, indeed, they 

 have not a relation of cause and effect. The enormously expanded 

 peronecranon reaches half way up the femur. The thigh is perma- 

 nently abducted and rotated outward. 



(a'. — From the body ; " long.") 



Discretion of ectoglutajus from the femoral group leaves only the 

 following muscles to be considered in this connection : — 



Psoas magnus. — Small, with distinct origin above, from the two 

 lowest lumbar vertebra? ; but inseparably blended, before passing the 

 brim of the pelvis, with the iliacus. (Description resumed below.) 



COMMUNICATIONS ESSEX INSTITUTE, VOL. VI. 21 April, 1871. 



