12 THe MICROSCOPE. 
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ELEMENTARY DEPARTMENT. 
A COURSE IN ANIMAL HISTOLOGY. 
SEVENTH PAPER. 
FRANK W. BROWN, M. D. 
ARTILAGE.—Three varieties of cartilage can be described :— 
(1) hyaline, (2) fibrous, and (3) elastic cartilage. The 
differences in structure found in the three sorts are confined almost 
entirely to the intercellular substance, the cells being nearly alike in 
all the forms. 
Hyarine Cartinace.—With a razor wetted with salt solution, 
make thin sections from the articulating surface of a fresh long 
bone. The head of the femur from a frog or young kitten will 
furnish most delicate specimens. Mount one of the sections in the 
salt solution and examine with alow power. The cells, large, gener- 
ally round though of various shape, will be seen scattered about in 
little groups of three or four through a homogeneous basement or 
intercellular substance. Near the periphery these cells are arranged 
somewhat parallel to the surface, whilst deeper down they are more 
irregularly disposed. Hach cell is composed of a delicately granular 
protoplasm containing a round, well-defined nucleus. At the peri- 
phery the cells are sometimes found provided with branched pro- 
cesses showing their development into connective-tissue cells of 
the synovial membrane. The cell protoplasm in mature cartilage 
(never in embryonal or infant life) generally contains some fat 
either in the form of granules or small drops. Although the cell 
possesses no membrane, it is inclosed by a delicate structureless 
capsule within a space called a lacuna. In living cartilage the cell 
entirely fills this lacuna, but after death it shrinks away from the 
capsule, showing that it was free within the lacuna. Articular car- 
tilage is not covered by any well-marked membrane, but all other 
cartilages are inclosed by a membrane, the perichondrium. 
Make a section from a costal cartilage, stain with carmine and 
mount in glycerine. This cartilage is of the hyaline variety, the 
intercellular substance being apparently structureless. The peri- 
chondium is seen to be composed of closely-knit bundles of fibrous 
tissue together with a small number of elastic fibrils. Small blood- 
vessels are also found in the membrane. These blood-vessels may 
pass through or into the cartilage, but are not distributed to its 
substance. 
