30 Oa the Restoration of Sight. 



fragment of this same bone in the osseous envelopment, and 



sometimes none at all. 



There are other examples of the destruction of more or 

 less considerable portions of bone. Ruysch remarked in 

 those individuals who had received a fracture of the neck of 

 the thigh bone, and which had not been cured, that the 

 heads remaining in the cotyloidal cavity had so far dimi- 

 nished in size, that they were almost reduced to nothing. I 

 have equally observed in some subjects in whom the rotuLi 

 was broken transversely, that the portion of the bone at- 

 tached to the ligament of the tibia was diminished in size in 

 a singular manner, as well as that attached to the extremities 

 of the extensor muscles of the leg, but the latter in a pro- 

 portionably less degree. In all these cases, it is for want 

 of nourishment that the parts decrease, and this nourish- 

 ment diminishes or ceases as soon as the circulation of the 

 nutritive matter slackens or is interrupted. And it is this 

 which takes place when the lymphatics, or blood-vessels, or 

 the nerves, are compressed or destroyed. May we not 

 ascribe to this cause the diminution which takes place, after 

 birth, of the liver in general, and of the left lobe in parti- 

 cular ? The diminution happens from this ; that the blood, 

 which was conducted there by the hepatic artery and by 

 the portatory and umbilical veins, is no longer removed by 

 the latter vein, and which was principally distributed through 

 the left lobe. Anatomists have remarked, that in the foetus, 

 the super-renal bodies and their blood-vessels were very 

 great relatively to the kidneys and the vessels, but that after 

 birth the vessels of the super-renal bodies diminish, and 

 those of the kidneys grow large in proportion : this occa- 

 sions the diminution in volume, and even the annihilation 

 of the former parts and the increase of the others. I do not 

 doubt that the thymus is effaced in a similar manner. It is 

 certain that it loses its volume in proportion as its arteries 

 contract ; and is it not because the lungs receive incompa- 

 rably more blood after birth than before, that the vessels of 

 the thymus, with which the pulmonary vessels are connected, 

 receive less blood also, and therefore at last disappear? 



There is another example of a no less remarkable destruc- 

 tion, 



