STRUCTURE OF THE HUMAN BODY 41 



7. Another primary tissue, or modification of cellular 

 structure, is termed the cartilaginous. (This seems to be a 

 substance intermediate between membrane and bonej It is 

 firm, smooth, highly elastic, of a pearly white colour, and ex- 

 cept bone, the hardest part of the animal frame. It is des- 

 titute of red vessels, and neither nerves nor lymphatics have 

 been discerned in it ; though as it becomes highly sensible, 

 like the fibrous tissue, by disease, it no doubt is supplied with 

 nerves*} It is placed at the ends of the bones, particularly 

 about the joints, where by its smooth surface, it facilitates 

 motion, and by its yielding nature, prevents the shock or jar 

 which would be produced were the same kind and degree of 

 motion effected by a rigid and inflexible substance. Where 

 strength and flexibility are required to be united * we there 

 find cartilage, as in the spinal column, between the ribs and 

 breast bone, in the larynx, the ear, nosej&c. 



Portions of cartilage seen in section. 



8. ClBy immersing cartilage in nitric acid and then in wa- 

 ter for some little time, we find its intimate structure so un- 

 folded, that we can perceive it to be composed of an infinite 

 number of minute fibres, arranged perpendicularly like the pile 

 of velvet^ Thus we see that in the construction of the joints, 

 millions and millions of springs of the most curious and ex- 

 cellent contrivance stand perpendicular to the direction of 

 the force applied, bend to pressure, and on its removal, regain 



