184 MANUAL OF HISTOLOGY. 



These granules especially are coloured red when heated with Millon's 

 reagent (Rkeiner). The fibres of hyaline cartilaginous tissue yield 

 chondrin likewise, as far as we can gather from investigations which have 

 been made up Jo the present. 



From all this we learn that hyaline cartilage is a tissue yielding 

 chondrigen with cells of a different constitution, with which we are not 

 more nearly acquainted. 



HI. 



Now, concerning elastic or reticular cartilage, we may obtain from it, 

 that is, from the residue of hyaline matter which it still contains, a small 

 quantity of chondrin, but only after long-con tinued*boiling. The elastic 

 fibres, which must take their rise from a metamorphosis of the chondrigen, 

 manifest here the same characteristic insolubility as elsewhere. It is only 

 after digestion in potash of many days' duration that they become jelly- 

 like and break down into granules, which are dissolved on the addition 

 of water. Whether the cells of reticular cartilage are more soluble than 

 those of the hyaline species, as has been stated, but without sufficient 

 foundation, requires more accurate investigation. 



Passing on then to fibro-cartilage, we find that its ground-substance 

 gives the same reactions as connective-tissue, and is transformed like- 

 wise into glutin by boiling. The latter is not, however, chondrin, but 

 the ordinary glutin of connective-tissue (p. 22). The semi-lunar cartilages 

 of the knee-joint are said to be most difficult of solution. 



At present we know nothing of the fluid with which cartilaginous 

 tissue is saturated. But the so variable proportion of mineral matters 

 which are found in the latter seem to point to a variation also in its 

 composition. Leucin, glycin, and cartilage-sugar may probably be re- 

 garded as physiological products of the transformation of the tissue in 

 question. Comp. 31, 33, and 22. 



The percentage of water in this tissue is reckoned at 54-70 per cent, 

 and the fats, which are entirely absent in no cartilaginous structures 

 from the very earliest periods, are found to vary naturally very con- 

 siderably. Their proportion, according to most observers, is about from 

 2 to 5 per cent., but which of their varieties occurs in the tissue of car- 

 tilage has not yet been ascertained. 



There now only remain for consideration the mineral constituents. 

 The proportions of these are very differently stated, which is, most pro- 

 bably, dependent on the imperfect methods of calcining which have been 

 resorted to. Phosphate of calcium and magnesium, with chloride of 

 sodium, carbonate of sodium, and sulphates of the alkalies, have been 

 mentioned as occurring here. 



We may set down a few results here which have been obtained in one 

 and the same animal as examples of the relative proportions of mineral 

 constituents. Schlossberger found that the ashes yielded by the nasal 

 cartilages of an old rabbit amounted to 3 '51 per cent., those of the ear 

 to 2*30 per cent., while those of the ribs rose to 22-80 per cent. Hoppe 

 again obtained from the costal cartilage of a suicide aged 22, 2 '20 per 

 cent., and from that of the knee-joint, 1*54 per cent, of ash. 



The observations which have been made on the costal cartilages of 

 the human being teach that the proportion of inorganic constituents is 

 increased in one and the same cartilage by age. The following analysis, 

 with the exception of the fifth, have been all made by Bibra : 



