130 REPORT — 1855. 



more widelj^ extended, to the great advantage of the student. This is especially 

 applicable in the homology of the osseous fishes, where, it is conceived. Professor 

 Owen has misapprehended the homology of the limb, functionally as well as struc- 

 turally. 



When the British Association first met in Glasgow, 1840, the author submitted a 

 scheme of the homology of the Cod and Haddock, demonstrating the pectoral fin as 

 the homologue of the hind-leg, and not the arm, as proposed by Professor Owen ; 

 and also that the round head of the femur was received into an acetabulum of a coxa, 

 which was connected with the cranium ; and also, that what Cuvier and others had 

 described as the scapula and clavicle, was really the femur and tibia, and that the 

 fibula, from being inside of the reversed leg, was described as a new bony segment — 

 epicoracoid ; the foot was then described as the arm, forearm, carpus and hand, 

 thus making two bones into the scapula, and multiplying one into several. A care- 

 ful study of the skeleton of the human foot would very readily have shown the ana- 

 logy which the tarsus bears to the bones of the arm ; the astragalus = brachium, 

 calcis =: ulna, scaphoid = the radius, the cuneiform and cuboid = the carpus. The 

 phalanges of the toes and fingers are easily seen to be identical. Functionally, the 

 hind-lirab in the Vertebrata is more or less associated with the sexual system ; in 

 the osseous fishes the pubis is widely separated from the pelvis, and is really homo- 

 typical of the sternum. It there is represented by the ventral fins. It appears in 

 the Cetacea in a similar relation, also connected with the sexual organs. 



It may be asked, where then is the homologue of the arm ? this is easily seen in 

 the opercular bones, which are here also connected with the respiratory system of the 

 osseous fishes. It is entirely different in the Chondria or cartilaginous fishes, where 

 the opercular bones are more in accordance with the higher animal types of terres- 

 trial animals as motor limbs, while the pectoral fins are sent further back, forming 

 the claspers of the rays and sharks. In those singular fishes, the Lophidse, there 

 may be traced an approach to the limb-form of the opercular bone, by the par- 

 tial development of some fin-rays in the substance of the skin, but not protruding 

 beyond its surface, at once forming the connecting link between the true osseous and 

 cartilaginous fishes, which zoologically considered form separate and distinct classes. 

 Geoffroy St. Hilaire was even further from the true homology of the opercular bones 

 •when he stated them to be the analogues of the auditory series, not perceiving that 

 these are also arranged in accordance with the law of organic unity of plan, capable 

 of modification by the necessities of each class of animals, and appearing in a vast 

 variety of metamorphic types. The idea of Professor Owen, that the arm of man 

 was merely the divergent apophysis of the occipital bone, is regarded as incon- 

 sistent with strict anatomy and function. All anatomists allow that the con- 

 struction of the skeleton is regulated by and dependent upon the nervous system, 

 ■whether in its original and primitive development in the foetus, or in mature condition 

 in the adult types. The skeleton has been described as the hard envelope protect- 

 ing the neural axis and its primary branches ; therefore the different limbs or mem- 

 bers can only be connected with that part of the caulon from whence the nervous 

 cords are emitted ; in that view the arm has no connexion with the occiput, but 

 with the lower part of the cervical and upper dorsal regions, through which the 

 nerves forming the brachial plexus are transmitted. The same holds true with 

 regard to the other membranal laminae, and also the primary costal laminae ; and it is 

 interesting to notice how strikingly this is demonstrable in the parietes of the chest, 

 where the intercostal nerve passes out from the cerebro-spinal axis under the protect- 

 ing lib, till it emerges in the region of the lower ribs near the distal part of the 

 dimal portion, to be distributed on the upper abdominal parietes in a manner similar 

 to the distribution of the nerves of the arm emerging from the interosseous space to 

 supply the hand. 



The true homology may be claimed as a qutestio vexata among anatomists ; but if 

 a careful examination of a vertebral skeleton in connexion with the distribution of the 

 nerves be patiently conducted, there is little doubt that the scheme now sub- 

 mitted will be found not only the most simple and easy of application, but also 

 most consistent with the structure of the vertebral skeleton. Having for twenty years 

 steadily examined the subject, and being completely satisfied with the correctness 

 of the explanation, the author cannot believe that the homology proposed by Cuvier, 



