40 AtflMAt PHYSIOLOGY. 



plete power of handling and fingering, are all found among 

 the lower animals. 



21. Skeletal Textures. The textures found in the skeleton 

 are bone, cartilage, and the fibrous tissues. The fibrous 

 tissues have been already considered. Bone, which is the 

 prevalent texture in the adult skeleton, makes its first ap- 

 pearance always either in cartilage or fibrous tissue, more 

 frequently in cartilage ; therefore, it is convenient to explain 

 the nature of cartilage first. 



Cartilage, in its most frequent form distinguished as true or 

 hyaline cartilage, is a firm texture capable of a marked amount 

 of flexion, but breaking with a smooth fracture when it is sought 

 to bend it further than its flexibility will allow. It presents, 

 tinder the microscope, a clear or slightly granular matrix, 

 with nucleated corpuscles imbedded in it, of variable size, and 

 lodged, singly or in groups, in hollows, which are either of a 

 rounded form, or with flattened sides and rounded angles, 

 and are never branched. The limits of these hollows are 

 denser than the surrounding matrix, and are termed capsules 

 of the corpuscles. Cartilage is completely devoid of blood- 

 vessels, for though occasional vessels occur in large masses, 

 as, for example, in the costal cartilages, they are always lodged 

 in canals along with a small amount of connective tissue. 

 But the matrix is freely permeated by nourishment from the 

 vessels round about; for cartilage is capable of rapid growth, 

 and its growth is marked by changes throughout its substance. 

 In growing cartilage, the corpuscles are seen in groups in 

 every stage of multiplication. One will be found with two 

 or more nuclei; another partially divided into two or more 

 parts, with septa springing up between them; while, in 

 other instances, the septa are completed, and exhibit various 

 thicknesses of matrix between them, towards which the 

 divided corpuscles still present flattened sides. The matrix 

 of cartilage is converted by prolonged boiling, not into gela- 

 tin, but into chondrin, a closely allied substance, which, like 

 gelatin, dissolves in hot water, and forms a jelly on cooling ; 

 but which differs slightly in composition, and has some 

 distinctive chemical reactions. This is the more remarkable, 

 as bone yields by boiling, not chondrin, but gelatin. 



The coating of cartilage on surfaces of bone which glide 



