1-16 



LECTURE VI. 



tion of the same parts, in the higher species. But these analogies 

 have been frequently overstated, or presented under unqualified me- 

 taphorical expressions, calculated to mislead the student and to ob- 

 struct the attainment of true conceptions of their nature. We should 

 lose some most valuable fruits of anatomical study were we to limit 

 the application of its facts to the elucidation of the unity of the 

 Vertebrate type of organisation, or if we were to rest satisfied with 

 the detection of the analogies between the embryos of higher and the 

 adults of lower species in the scale of being. We must go further, 

 and in a different direction, to gain a view of the beautiful and fruit- 

 ful physiological principle of the relation of each adaptation to its 

 appropriate function, and if we would avoid the danger of mistaking 

 analogy for homology or identity, and of attributing to inadequate 

 hypothetical secondary causes the manifestations of Design, of supreme 

 Wisdom and Beneficence, which the various forms of the Animal 

 Creation offer to our contemplation. 



To revert, then, to the skeleton of Fishes, with a view to the teleo- 

 logical application of the facts determined by the study of this com- 

 plex modification of the animal framework. No doubt there is analogy 

 between the cartilaginous state of the endo-skeleton of Cuvier's 

 Chondropterygians, and that of the same part in the embryos of air- 

 breathing Vertebrates ; but why the gristly skeleton should be, as it 

 commonly has been pronounced to be, absolutely inferior to the bony 

 one is not so obvious. The ordinary course of age and decrepitude, or 

 of what may be called the decay of the living body, is associated with 

 a progressive accumulation of earthy and inorganic particles, gradually 

 impeding and stiffening the movements, and finally stopping the play 

 of the vital machine. And I know not why a flexible vascular 

 animal substance should be supposed to be raised in the histological 

 scale because it has become impregnated, and as it were petrified, by 

 the abundant intus-susception of earthy salts in its areolar tissue. It 

 is perfectly intelligible that this accelerated progress to the inorganic 

 state may be requisite for some special office of such calcified parts in 

 the individual economy ; but not, therefore, that it is an absolute ele- 

 vation of such parts in the series of animal tissues. 



It has been deemed no mean result of Comj)arative Anatomy to have 

 pointed out the analogy between the shark's skeleton and that of the 

 human embryo, in their histological conditions ; and no doubt it is a 

 very intei'csting one. But can no insight be gained into the purpose of 

 the all-wise Creator, in so arresting the ordinary course of osteogeny 

 in the highly organised fish ? Are we to entertain no other view of 

 it than as an unfinished, incomplete stage of an hypothetical serial 

 development of organic forms ? 



