TISSUES OF THE BODY. 



169 



bones entering into the formation of joints, and membranous, or such as 

 serve for the formation of cavities, in that they strengthen and solidify 

 the walls of the latter. 



Another classification based on the length of existence of the tissue 

 might be said to be natural. We meet, namely, early in intra-uterine 

 life and very widely distributed, a cartilaginous skeleton, the greater 

 part of which disappears in the normal process of development at an 

 early period, being destined to give place by decay to another tissue, 

 namely, bone, whilst only a small portion is retained throughout the 

 whole of life. The first of these is temporary, the second permanent car- 

 tilage (!)._ 



There is, however, a third and more rational classification, which is 

 based on the histolcgical texture of the cartilage or that of its inter- 

 cellular substance. 



The latter appears originally in all cartilages, homogeneous, transpa- 

 rent, or slightly clouded. This transparent constitution may last the 

 whole life through, when such cartilages are known as hyaline, and 

 represent the typical form of the tissue (fig. 157). These may be re- 

 cognised by the unaided eye, from their appearing in thin slices, trans- 

 parent as water, while in larger or thicker masses they present a bluish- 

 white or at times milky appearance. 



Fig. 157. Hyaline cartilage. 



Fig. 158. Rcticuiar cartilage, 

 from the human epiglottis. 



Cartilaginous tissue is, however, liable to undergo in the course of 

 time many kinds of anatomical metamorphoses even of the inter- 

 cellular substance, which in some cases 

 commence very early, in others how- 

 ever delay a long time in making their 

 appearance. At one time again, they 

 affect but small portions of a cartil- 

 age, and at another extend themselves 

 over the whole of the latter. If they 

 appear early and spread throughout 

 whole cartilages, they produce special 

 modifications of the latter and are speci- 

 ally named. 



Thus intercellullar substance may 



undergo a coarsely granular clouding, Fig- 159. 



or become streaky and banded, or be transformed into fibres of various 

 kinds. At one time we perceive a partial change into parallel bands and 

 fibres unacted on by acetic acid ; at another, meet with an interlacing of 

 dark elastic fibres, or remark in the matrix the characteristic, delicate 



