136 THE OSTEOLOGY AND MYOLOGY 



correlation of the muscular system with the movements and habits of the animal. It is 

 desired, however, to offer in the present connection, as somewhat of a supplement to 

 what has preceded, some thoughts upon questions of antero-posterior symmetry which have 

 forced attention during the writer's dissections. 



" If," as a distinguished anatomist has said, " antero-posterior symmetry can be shown to 

 exist in the bones, then we can feel some confidence that whatever the difficulties at present 

 may be with regard to the muscles, nerves and vessels, they will sooner or later be over- 

 come." We believe that antero-posterior symmetry not only can be, but has been, demon- 

 strated in the bones of the limbs of higher vertebrates, in the sense that, for instance, 

 makes a humerus and a femur mutually correspondent : — the one a reversed representative 

 of the other. Few, if any, anatomists to-day deny the main point, however widely they 

 may differ in the details of their comparisons of fore and hind limbs as symmetrical repeti- 

 tive parts of the skeleton. And if an arm and a leg are found correspondent as to their 

 osseous structure, it seems to follow — we had almost said as a matter of course — that cor- 

 respondence, similar in kind if not in degree, exists in the other tissues and organs, sur- 

 rounding, nourishing, protecting and acting upon the bony framework. Assuming, then, 

 without argument, the existence of special osteological homologies in limbs as a demonstrated 

 fact, we infer similar existence of homology in the muscles, as a logical sequence. But the 

 difficulty of directly proving such an inference to be true, is very great ; so great, that the 

 pointing out of muscle for muscle throughout the limbs has not yet been done, and perhaps 

 never will be. Part passu as we advance from the bare skeleton — the simple framework 

 of the body — modifications of an ideal type increase in number and degree of complexity. 

 Teleology may so far overshadow morphology that only glimpses, as it were, of original 

 unity of plan can be discerned in the obscurity ; or we may even be left in total darkness. 

 But to the imperfection of our vision, perhaps, rather than to want of the whereupon to 

 exercise it, may be ascribed our shortcoming in this respect ; and if only one single ray of 

 light be afforded us, it should encourage us to hope and seek for more. And I believe that 

 we have at least one clear and steady beacon light to guide us in our search for the special 

 homologies of the muscles of the limbs. This is found in the extensor muscle of the fore- 

 arm and leg. The proposition, which appears almost axiomatic, may be thus stated : — If the 

 humerus and the femur are in any sense correlated and correspondent, then the triceps 

 extensor cubiti and the triceps extensor cruris are in the same sense correlated and corres- 

 pondent. 



Before any attempt is made to determine muscular homologies, a clear understanding of 

 the homology of the several bones of the limbs is obviously necessary. Without repeating 

 the arguments with which anatomists have for so many years defended their conflicting 

 views with more or less success, it will be sufficient to present, in tabular form, the special 

 homology of the bones that will be made the basis of the present inquiry into the corres- 

 ponding relations of the muscles. Professor Wyman's method of viewing the skeleton is 

 the one followed, except in the case of the coracoid and clavicle, as related to the ischium 

 and pubis ; in which instances Professor Owen's determination is adopted. The skeleton 

 18 suspended horizontally, the limbs depending vertically, each segment a little flexed, with 

 the forearm supine, and the palm downward. In this position the scapular arch may be 

 considered to point forward, and the pelvic backward ; the arm points backward and the 

 thigh forward ; the forearm forward and the leg backward ; the hand backward and the 



