Sept. 9, 1875 



NATURE 



415 



are the most irregular structuies imaginable. Even in the 

 sacrum and in the rest of the column the amount of variation 

 finds no jiarallel in other animals. In the skull, except in some 

 of the lowest forms of humanity, the dorsum selhc is a ragged, 

 warty, deformed, and irregular structure, and it never exhibits 

 the elegance and finish seen in other animals. The curvature of 

 the skull and shortening of its base, which have gradually 

 ittcrcased 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 pro- 

 duces such a set of unsymmetrical and rugged performances as 

 is quite peculiar to man ; and to the human anatomist many 

 other examples of similar phenomena will occur. 



Questions of homology are matters which must be ever pre- 

 sent in the study ol 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 in this country during the 

 last twenty-five years by referring shortly to the homological 

 writings of three eminent anatomists —Professors Owen, Goodsir, 

 and Huxley. 



Changes of Opinion on Morphological Subjids. 



For the first time in English literature the great problems of 

 this description were dealt with in Prof. Owen's work already 

 referred to, published in 1848 ; and it is unnecessary 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 justly and quietly 

 corrected by Goodsir at the meeting of this Association in 1856 

 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 underlying 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 ualenability of Prof. 

 Owen's theory of the connection of the shoulder-girdle with the 

 occipital bone, and pointed out that the limbs were not appen- 

 dages of single segments corresponding with individual vertebra;. 

 Referring to the development of the hand and foot, he showed 

 the imporlance of observing the plane in which they first appear, 

 and that the thumb and great toe are originally turned towards 

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

 the vertebral column. But he probably went too far in trying 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 vertebras 

 becomes altered as the surface of the body is approached — a 

 truth illustrated in the vertebral columns of the plagiostomatous 

 fishes, in the muscle-segments over the head in the p euronectids, 

 and in the interspinal bones bearing the dorsal and anal finrays 

 of numbers of fishes, but, so far as I know, not hitherto sufficiently 

 appreciated by any anatomist. 



In 1858 Prof. Huxley delivered his Croonian Lecture on 

 the vertebrate skull, and in 1863 his lectures at the Royal College 

 of Surgeons on the same subject. He profited by the wisdom 

 of Goodsir, and studied the works of Ralhke, Reicheit, and 

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

 further t'^an Goodsir. He assumed from the first that the homo- 

 logies of adult structures could be determined by development, 

 and that by that study alone could they be finally demonstrated. 

 As regards the skull, the constitution of which always remains 

 the central study of the vertebrate skeleton, his writings marked 

 the introduction of a period of revulsion against not only the 

 systems of serial homologies previously suggested, but even 

 against any attempt by the study of the varieties of adult forms 

 to set them right. Mr. Huxley has added materially to the 

 previously existing number of interpretations as to what elements 

 correspond in different animals, ,and in doing so has found it 

 necessary to make various additions to the already troubled 

 nomenclature. Those who consider these changes correct will 

 of course see in them a prospect of simplicity to future students ; 

 but to those who, Ike myself, have never been able to agree with 

 them, they are naturally a source of sorrow. Among the changes 

 referred to may be mentioned the theory of the ^'periotic bones." 

 That theory, I venture to think, a very unfortunate one, intro- 

 ducing a derangement of relations as widespread as did Good- 



sir's theory of the frontal bone. And do not think me presump- 

 tuous in saying so, seeing that this theory is in antagonism with 

 the identifications of every anatomist precedmg its distinguished 

 originator, not excepting Cuvier and Owen ; nor is it easy to 

 discover what evidence it has to support it against the previously 

 received decision of Cuvier as to the external occipital and mastoid 

 of fishes. Without entering into the full evidence of the subject, 

 it may be stated that, so far as this theory affects the alisphinoid 

 in the skull of the fish, it must be given up, and the determination 

 of Prof. Owen must be reverted to, when it is considered 

 that in the carp the third and fourth nerve pierce what that 

 anatomist terms the orbitosphenoid, the bone which is alisphenoid 

 according to the theory which terms the alisphenoid of Owen the 

 prootic. A proof still more striking is furnished by Malapterurus 

 and other Silurids, in which the bone in question is pierced by 

 the optic nerve. That being the case, the prootic theory will be 

 seen to have arisen partly from giving too much importance to 

 centres of ossification, and partly from considering the nerve- 

 passage in front of the main bar of the alisphenoid of Owen as 

 corresponding with ihe/orame>i ovale of man rather than with the 

 foramen rotundum and sphenoidal fissure. A spiculum, however, 

 separating the second from the third division of the fifth nerve, 

 and having therefore the precise relations of the mammalian 

 alisphenoid, does exist in the carp and other fishes. But in 

 reptiles Prof. Huxley's determination of the alisphenoid is 

 right, and Prof. Owen's clearly wrong ; for in the crocodile 

 the alisphenoid of Huxley and others is perforated by the sixth 

 nerve, so that it cannot have any claim to be called orbiiosphenoid. 

 I must, however, maintain, against Prof. Huxley's view. Prof. 

 Owen's determination of the nasal in fishes, notwithstanding that 

 Prof. Owen has failed to appreciate the exact relation of 

 that bone to the nasals of mammals, and has thereby laid his 

 position open to attack. The arguments on that point Prof. 

 Huxley was good enough to lay before the public fourteen years 

 ago, by kindly reading for me before the Royal Society a paper 

 which subsequently appeared in its " Transactions ; " and I am 

 not aware that anyone has since attempted to controvert 

 them. 



I shall not trouble you further with such matters of detail ; 

 but it will be clear from what has been said that the beginner in 

 comparative anatomy must at the present day find himself at the 

 outset, in the most important part of his osteological studies, 

 faced with a diversity of opinion and confusion of nomenclature 

 sufficient to produce much difficulty and to have a repelling 

 effect on many minds. Such difficulties might well be en- 

 countered with enthusiasm where a belief existed that behind 

 them lay a scheme of order and beauty ; but not many will spend 

 time in investigating such intricate details if they doubt the interest 

 of the general conclusions likely to be reached by mastering them. 

 On this account it is a great pity that the scepticism generated 

 partly by the difficulties of the subject, and partly by reaction 

 from the dogmatism of the admirers of Oken, does too frequently 

 discourage the investigation of the serial homologies of the parts 

 entering into the segments of the skull, and the determination of 

 the nature and number of those segments. It is a pity that so 

 much clamour has been made for a number of years against the 

 expression "vertebral theory of the skull," because fighting 

 against words is but stupid warfare at the best, and because a 1 

 that was really meant, and could be justly stated, could have 

 been brought into prominence without objecting to a time- 

 honoured phrase. It is questionable if anyone who ever used 

 the convenient term "vertebral theory " meant to indicate more 

 than a certain community of plan on which were built the 

 segments of the skull as well as those of the spinal column ; that, 

 in fact, the two constituted one complete chain, of which the 

 first few segments were so different from the rest, that till Oken 

 pointed the fact out, it was not recognised that they were 

 segments lying in lineal continuity with the rest. But the matter 

 has recently stood thus : — that to some minds, in the imperfect 

 state of our knowledge, one thing seemed essential to a segment 

 compatable to the rest, and to others something else seemed 

 requisite ; and the oddity of the position of affairs is this, that 

 the objectors to the phrase "vertebral theory " have been as 

 crotchety in setting up imaginary essentials to a segment as their 

 neighbours. On tlie one side we were taught to expect certain 

 definite osseous elements in each segment, to which definite 

 names were given ; while, on the other, in opposition schtm^s, 

 centres ol ossification have been built on as matters of primary 

 consequence, although a glance at the modifications in the 

 vertebral column proper might convince anyone that they are 

 things of the very slightest importance morphologically. Ako 



