92 LOCOMOTION. [CHAP. iv. 



composed of clearly defined and roundish nucleated cells, huddled 

 together, as it were, in a promiscuous manner, fig. 16. In spe- 

 cimens from persons of adult age, the cells have frequently a fine 

 granular opaque matter sprinkled on their exterior ; and these, in 

 older subjects, are seen to have become minute centres of a spurious 

 ossification. 



In the cartilage of the ear the cells are small, and very close to 

 each other; in shape they are very uniform, and vary in size from 

 fsVo to TOO f an " lc k- A pi ece f tn i s cartilage, when examined 

 by a high power, has very much the appearance of a sieve ; the 

 holes of which are occupied by nuclei and their nucleoli. The 

 intercellular substance is not exactly white fibrous tissue ; but so 

 nearly resembles it, especially towards the surface, as to make this 

 form of cartilage approach fibro-cartilage more nearly than does 

 any other. 



The membraniform cartilages are invested by a layer of white 

 fibrous tissue, containing blood-vessels, and called the perichondrium. 

 Its fibres are densely interwoven in all directions, and adhere inti- 

 mately to the intercellular substance of the cartilage. This invest- 

 ment corresponds with the periosteum of bone, and in the tempo- 

 rary cartilages is indeed the very same structure. It is a nidus for 

 the nutrient vessels of cartilage, and often serves to give attachment 

 to muscles. It is best examined on the cartilages of the ribs. Its 

 great toughness is sometimes well displayed in fractures of these 

 cartilages, where the perichondrium remains untorn between the 

 fragments. 



The articular cartilages, which have no perichondrium, are sup- 

 ported and supplied with blood by the bone to which they are 

 adapted, and by the synovial membrane, which always passes for 

 at least some little distance over their free surface. 



Vessels of Cartilage. Speaking in general terms, cartilage may 

 be styled a non- vascular substance, for considerable masses of all 

 its varieties exist, unpenetrated by a single vessel. The term non- 

 vascular, however, it is important to observe, is to be understood in 

 a relative sense. All tissues deriving their nutriment from blood- 

 vessels, are, in fact, if traced up to their microscopic elements, on 

 the outside of the channels through which the blood flows. If the 

 quantity of vessels be large in proportion to the tissue, or if the two 

 are mingled in an intimate manner, we term the part very vascular. 

 If, on the other hand, there be a considerable mass of tissue, among 

 the elementary parts of which no vessels penetrate, it is styled non- 

 vascular. This word is not used in an absolute sense : for, if so, 



