TRANSACTIONS OF THE SECTIONS. 137 



is in the lower auiuials. Look at the coccygeal A-ertebroe ; they are the most irre- 

 gular structures imaginable. Even in the .sacrum and in the rest of the column the 

 amount of variation iiniis no parallel in other animals. In the skull, except in some 

 of the lowest forms of humanity, the dorsiun selUe is a ragged, warty, deformed, and 

 irregular structure, and it never exhibits the elegance and finish seen in other ani- 

 mals. The curvature of the skull and shortening of its base, which have gradually 

 increased in the ascending series of forms, have reached a degree which cannot be 

 exceeded ; and the nasal cavity is so elongated vertically, that in the higher races 

 nature seems scarcely able to bridge the gap from the cribriform plate to the palate, 

 and produces such a set of unsj^mmetrical and ruggeil performances as is quite pecu- 

 liar to man ; and to the human anatomist many other examples of similar pheno- 

 mena will occur. 



Questions of homology are matters which must be ever present in the study of 

 structure, as distinct from function — both the correspondence of parts in one species 

 to those in others, and the relations of one part to another in the same animal ; and 

 perhaps I shall best direct attention to the changes of opinion on morphological 

 subjects iu this country during the last twenty-five years by referring shortly to the 

 liomological writings of three eminent anatomists — Professors Owen, Goodsir, and 

 Huxley. 



For the first time in English literature the great problems of this description 

 were dealt with in Professor Owen's work already referred to, published in IBiS ; 

 and it is uimecessary to say that, notwithstanding the presence of unquestionable 

 errors of theory, that work was a most valuable and important contribution to 

 science. The faults in its general scope were j ustly and quietly corrected by Good- 

 sir at the Meeting of this Association iu 185(5 in three papers, one of them highly 

 elaborate ; and in these he showed that the morphology of vertebrate animals could 

 not be correctly studied while reference was made exclusively to the skeleton. He 

 showed the necessity of attending to all the evidence in trying to exhibit the under- 

 lying laws of structure, and especially of having constant regard to the teachings of 

 embryology. Among the matters of detail which he set right it may be mentioned 

 that he exposed the unteuability of Professor Owen's theorj' of the connexion of the 

 shoulder-girdle with the occipital bone, and pointed out that the limbs were not 

 appendages of single segments corresponding with individual vertebras. Referring 

 to the development of the hand and foot, he showed the importance of observing 

 the plane in which they first appear, and that the thumb and great toe are originally 

 turned toward the head, the little finger and little toe toward the caudal end of the 

 vertebral column. But he probably went too far in trj'ing to make out an exact 

 correspondence of individual digits with individual vertebral segments, failing to 

 appreciate that the segmentation originally so distinct in the primordial vertebra 

 becomes altered as the surface of the body is approached — a truth illustrated in the 

 vertebral columns of the plagiostomatous fishes, iu the muscle-segmeuts over the 

 head in the pleuronectids, and in the interspinal bones bearing the dorsal and anal 

 fin-rays of numbers of fishes, but, so far as I know, not hitherto sufficiently appre- 

 ciated by any anatomist. 



Goodsir also exploded, one would have thought for ever, the erroneous theory of 

 the correspondence of the mammalian tympanic plate with the quadrate bone of 

 birds and the suspensorium of fishes, directing attention to the neglected but just 

 appreciation by St.-Hilaire of the homological importance of the ossicles of the ear, 

 and to the embryological work of Meckel and Heichert. But undoubtedly he fell 

 into great mistakes of his own in matters of detail connected with the exceedingly 

 diificult question of the correspondence of the bones of the skull, the principal of 

 these probably being an unfortunate notion that the f/reat frontal of fishes was a 

 bone which disappeared from the skulls of mammals, a notion which spread its 

 influence over his determination of a number of other elements, and introduced a 

 confusion which made his paper on the skull hard to understand. 



In 1858 I'rofessor Huxley delivered his Croonian Lecture on the vertebrate 

 skull, and in 1863 his lectures at the Royal College of Surgeons on the same sub- 

 ject. He profited by the wisdom of Goodsir, and studied tlie works of Rathko, 

 Reichert, and other embryologists. But, rightly or wrongly, he took a step further 

 than Goodsir. He assumed from the first that the homologies of adult structures 

 1875. 11 



