38 CARTILAGES AND THEIR STRUCTURE. 



of them in various parts of the body, though not from the ar- 

 ticular. 



When a recent cartilage is cut, a whitish juicy fluid is seen to 

 exude from its substance, which must get into it, by imbibition 

 from the surrounding parts, or as has been thought more proba- 

 ble, be carried into it, by white vessels, too small to admit more 

 than the serous portions of the blood. If inflammation take place, 

 which is admitted in many carlilages, though not as yet proven 

 to exist in those of the joints, it differs from ordinary inflam- 

 mation as these vessels are never so dilated, as to admit the 

 red globules, and present a red appearance. No lymphatics 

 have ever been traced into them, though Mascagni was 

 disposed to consider them as formed entirely of these vessels. 

 Nor have nerves been found in them, the very existence of 

 which in these parts, though so necessary to the perfection of 

 other organs, would have unfitted them for their office. Hence 

 we find them smooth, so as to move upon one another without 

 friction, destitute of nerves, so as to bear pressure without sen- 

 sation, and feebly supplied with vessels, so as to be little prone 

 to inflammation, if they be not, as Gerdy has suggested, a mere 

 secretion like the hair and .nails. Hence they are enabled to 

 bear exposure to the air for a considerable time without 

 change, as stated by Velpeau, and to exist unharmed frequently 

 in the midst of gangrene. 



According to J. Davy, their chemical composition is 55. parts 

 in the hundred of water, 44.5, of albumine, and .5 of phosphate 

 of lime. As in the bones, however, the chemical proportions 

 vary at the different periods of life. They are nearly fluid in 

 the foetus, contain a large amount of fluid in youth, have the 

 proportions given above at puberty, and a much larger amount 

 of earthy matter in old age. In fact, with some few exceptions 

 in the joints, they all have a natural tendency to ossify as life 

 advances. 



The structure of cartilage is, however, not fully understood ; that 

 they share in some manner in the general circulation of the body, 

 is rendered probable by their being colored yellow in jaundice ; 

 and that they are not reddened like the bones when an animal is 



HO ....... ---in 



