244 ANATOMY OF VERTEBRATES. 



logics, under all the various modifications by which they are 

 adapted to the several modes and spheres and grades of existence 

 of the different species — should be the great aim of anatomical 

 science ; as being that which reduces its facts to the most natural 

 order, and their exposition to the simplest expressions. 



It is impossible, in pursuing the requisite comparison upward 

 through the higher organised classes, not to recognise resemblances 

 between the ultimate states and forms of ichthyic organs, and the 

 transitory condition of the same parts, in the higher species. 

 But these resemblances have been sometimes overstated, or pre- 

 sented under unqualified metaphorical expressions, calculated to 

 mislead the student and to obstruct the attainment of complete 

 conceptions of their nature. We should lose most valuable fruits 

 of anatomical study were Ave to limit the application of its facts 

 to the elucidation of the unity of the vertebrate type of organi- 

 sation, 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 fruitful physiological 

 principle of the relation of each adaptation to its appropriate 

 function, if we would avoid the danger of resting in speculations 

 on the mode of operation of derivative secondary causes, and of 

 blinding the mental vision to the manifestations of Design which 

 the various forms of the Animal Creation offer to our contem- 

 plation. 



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

 teleological application of the facts determined by the study of 

 this complex 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 or teleologically inferior to the bony one is not so | 

 obvious. The ordinai'y course of age, decrepitude, and 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 I 

 intelligible that this accelerated progress to the inorganic state j( 

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



