ON THE BONES, &c. OF THE ANIMAL FRAME. 



113 



pour down a deluge over the mountains — and whole forests fall prostrate be- 

 fore its fury. Down rolls the gathering wreck towards the deep, and blocks 

 up the mouth of that very creek the seaman has entered, and where he now 

 finds himself in a state of captivity. How shall he extricate himself from 

 his imprisonment 1 — an imprisonment as rigid as that of the Baltic in the 

 winter season. But the hosts of the teredo are in motion : — thousands of 

 little augurs are applied to the floating barrier, and attack it in every direc- 

 tion. It is perforated, it is lightened, it becomes weak ; it is dispersed, or 

 precipitated to the bottom ; and what man could not effect, is the work of 

 a worm. Thus it is that nothing is made in vain ; and that in physics, as 

 well as in morals, although evil is intermingled with good, the good ever 

 maintains a predominancy. 



LECTURE XL 



ON THE BONES, CARTILAGES, TEETH, ARTICULATION, INTEGUMENTATION, HAIR, 

 WOOL, SILK, FEATHERS, AND OTHER HARD OR SOLID PARTS OF THE ANIMAL 

 FRAME. 



In a former lecture we took a general survey of the characteristic features 

 that distinguish the unorganized from the organized world, and the vege- 

 table kingdom from the animal: we examined into the nice structure of 

 plants, and the resemblances which they bear to the animated form. In our 

 last lecture we proceeded to an inquiry into the nature of the living principle, 

 took a glance at a few of the theories that have been invented to explain its 

 essence and mode of operation, and contemplated the origin and powers of 

 the muscular fibre, which may be denominated its grand executive organ. 



The muscles of an animal, however, are not the only instruments of animal 

 motion ; the bones, cartilages, and ligaments contribute very largely to the 

 action, and the skin is not unfrequently a substitute for the muscle itself. Thest, 

 therefore, as well as a variety of other bodies minutely connected with them, 

 or evincing a similarity of construction, — as the teeth, hair, nails, horns, 

 shells, and membranes, — are now to pass under our review, and are entitled 

 to our closest attention ; and I may add, that their diversity of uses and ope- 

 rations, and the curious phenomena to which they give rise, are calculated to 

 aff"ord not less amusement than instruction. 



I had occasion to remark lately,* that lime is a substance absolutely neces- 

 Bary to the growth of man. It is, in truth, absolutely necessary to the growth 

 of almost all animals ; even soft-bodied or molluscous worms, except in a 

 few instances, are not free from it ; nay, even infusory animals, so minute as 

 to be only discerned by the microscope, still afford a trace of it in the calcare- 

 ous specie which constitutes their snout ; but it is in the bones and shells 

 of animals that lime is chiefly to be found ; and hence those animals possess 

 most of it in whom these organs are most abundant. 



Bone, shell, cartilage, and membrane, however, in their nascent state, are 

 all the same substance, and originate from a viscid fluid, usually supposed to 

 be the coagulable lymph, or more liquid part of the blood ; which, secreted in 

 one manner, constitutes jelly, or gelatine, a material characterized by its solu- 

 bility in warm water, heated to about half the boiling point; and secreted in 

 another manner, forms albumen, or the material of the white of the egg, cha- 

 racterized by its coagulating instead of dissolving in about the same heat : the 

 difference, however, between the two, consisting merely, perhaps, in the dif- 

 ferent proportion of oxygen they contain. Membrane, is gelatin, with a 

 small proportion of albumen to give it a certain degree of solidity ; cartilage 



* Series i. Lect, vi. On Geolopy, p. 73, and passinn ; and Lect. viii. On Organized Bodies, and the 

 Structure of Plants compared to that of Animals, p. 81. 



H 



