ELEMENTARY STRUCTURE OF ORGANIZED BODIES. 



39 



cells, the intercellular spaces being filled with a more com- 

 pact substance, called the hyaline matter. Figure 4 repre- 

 sents a slip of cartilage from the horse, under 

 a magnifying power of one hundred and twen- 

 ty diameters. 



43. The osseous or bony tissue differs from 

 the cartilaginous tissue, in having its meshes 

 filled with salts of lime, instead of hyaline sub- 

 stance, whence its compact and solid appear- 

 ance. It contains, besides, minute, rounded, 

 or star-like points, improperly called bone- 

 corpuscles, which are found to be cavities or 

 canals, sometimes radiated and branched, as 

 is seen in figure 5, representing a section of a 

 bone of a horse, magnified four hundred times. 



Fig. 4. 



Fig. 5. 



44. The muscular tissue, which forms the flesh of ani- 

 mals, is composed of bundles of parallel fibres, which pos- 

 sess the peculiar property of contracting or shortening them- 

 selves, under the influence of the nerves. In the muscles 

 under the control of the will, the fibres are commonly 

 crossed by very fine lines or wrinkles ; but not so in the 

 involuntary muscles. Every one is sufficiently familiar with 

 this tissue, in the form of lean meat. 



45. The nervous tissue is of different kinds. In the 



nerves proper, it is composed of 



very delicate fibres, which return 



back at their extremities, and 



form loops, as shown in figure 6, 



representing nervous threads as 



they terminate in the skin of a 



frog. The same fibrous structure 



is found in the white portion of the brain. But 



the gray substance of the brain is composed of 

 very minute granulations, interspersed with clusters of larger 

 cells, as seen in figure 7. 



Fig. 7. 



Fig. 6. 



