42 STRUCTURAL UNITS OF HUMAN TISSUES 



cellular substance since it occurs between cells. The other 

 important forms of connective tissue are cartilage and 

 bone. 



Cartilage. — An examination under the microscope (see 

 Ex. XXVI. and Fig. 13) shows that cartilage, or gristle, 

 consists of a sohd mass surrounding pits very much after 

 the manner of Swiss cheese. The solid mass is the elastic 

 intercellular part of the connective tissue, and corresponds 



to the fibers of the intermus- 



^ cular form. The pits or la- 



/"S^y ounce are inclosed in capsules, 



vi)xr\ ^^^"" -"" and within these capsules lie 



v-^ \S? ■<: the cells which produce the 



fraj solid matter. These cells are 



(7^\(5)"- ""-— v» ^^® ^^^^ structural units of 

 rp$, (Cv) this form of tissue, and the 



solid part is made by them. 



P As this is thrown out by the 



' protoplasm of the cells, it col- 



FIG. I3-Hyaline cartilage; c^ ^ ^ ^^ ^^^ ^^ ^^^ ^^ 



capsule in a lacuna ; m, matrix ' 



formed by cells ; c, cartilage cell ; fomiS an important StrUCtUral 



"'"" ''"^" element of our bodies. For 



example, the external ear and the nose owe their shape 

 to underlying layers of this substance, while the ends of 

 the bones are capped by layers of the same material, and 

 thus protected from friction and jar. 



Bone. — If, in addition to the gristly matter given off 

 by the cartilage cells, there be added salts of lime, the 

 intercellular mass becomes hardened, and we have a struc- 

 ture called bone. An examination under the microscope 

 (see Ex. XXVI. and Fig. 14) shows that bone differs from 

 cartilage in that the intercellular mass is arranged in rings 



