170 MANUAL OF HISTOLOGY. 



fibrillce of connective tissue paling under the action of this reagent. The 

 two last-named varieties have given rise to the distinction between the 

 elastic or reticular cartilages (fig. 158), and the connective tissue or fibro 

 cartilage (fig. 159). Parts which have undergone metamorphoses of the 

 intercellular substance of this kind lose the bluish-white appearance of 

 hyaline cartilage, and become opaque and either yellow or white. 



REMARKS. Correctly speaking, this division is not good, in that we are unable 

 to draw any distinct line between permanent and temporary cartilage, and the ques- 

 tion is only as to differences of degree. Comparative anatomy teaches likewise that 

 the temporary cartilages of one group of animals may be permanent in another, and 

 vice versa. Finally, it is very frequently the case that late in life bony growths are 

 formed at the expense of the so-called permanent cartilage. 



104. 



The cells of cartilage manifest no less an inclination to change than 

 the intercellular substance. And though in very young tissue these 

 elements present nothing very striking in their appearance, yet they 

 may become very characteristic structures through subsequent transfor- 

 mation. 



In its rudimentary condition growing cartilage presents itself as a simple 

 aggregation of nucleated formative cells (flattened somewhat where they 

 are in contact with one another), between which close scrutiny enables us 

 to detect thin streaks of a homogeneous glistening substance. This con- 

 dition remains throughout life among the cartilages of lower animals. 

 Soon after this these streaks become broader, and within a short time 

 the interstitial matter may attain proportions as great as represented in 

 fig. 160. 



The cartilage cells now appear round, oval, or more or less crescentic in 

 form, and frequently very strongly flattened. Their dimensions, exclusive 

 of extreme cases, may be stated at 0'0182-0'0275 mm. The body of the 

 cell consists frequently of a homogeneous or delicately granular proto- 

 plasm without a membrane, and in it we almost 

 always find a simple vesicular nucleus, measuring 

 from 0-0075 to OO144. According to Rollett, this 

 protoplasm becomes clouded in a peculiar manner 

 on being heated up to 73-75 C. 



Under the action of reagents, and even of water, 

 the body of the cells of many cartilages may be 

 seen to assume jagged or stellate forms. Violent 

 Fij?. 160. Ceils of an em- electric discharges also cause the cells in question 

 Sage? rom m the r pig. car to take on the same forms, with a simultaneous de- 

 crease in size (Heidenhain, Rollett). They are also 

 probably endowed with vital contractility ; but this has not yet been 

 proved beyond doubt. 



The further changes to which the cell (fig. 161) is liable apply less to 

 the shape (which generally remains one of those mentioned) than to the 

 size, which increases, and at times to a very great extent. The nuclei 

 also frequently lose their vesicular nature, becoming solid while they re- 

 main smooth, or else assuming a granular appearance. Deposition of fats 

 in the body of the cell may also commence early. 



Another appearance, which is remarked not unfrequently in many 

 mature cartilages, though to a variable extent, is also of great significance. 

 Halos or rings of a sometimes homogeneous, sometimes laminated, sub- 



