CHAPTER XII. 



THE DUCTLESS GLANDS, THE LIVER, AND THE 

 KIDNEYS. 



IN the preceding chapters we have so far traced the history 

 of the blood, that we have seen how it is vitiated in the 

 tissues and oxygenated in the lungs, and how it is replenished 

 with material both from the waste of the tissues and from 

 the digested food; we have noted one source of origin of the 

 corpuscles, and studied the purification from carbonic acid. 

 But there still remain for consideration various processes of 

 elaboration and depuration carried on by the spleen and 

 other ductless glands, by the liver, and by the kidneys. 



120. The Ductless Glands. Under this head are grouped 

 the spleen, the thyroid and thymus glands, the suprarenal 

 capsules, and also the lymphatic glands and the closed 

 follicles of the digestive tube, both of which have been 

 already considered (pp. 103 and 153). 



The thyroid body is a limited structure, consisting, in the 

 human subject, of two lobes joined together by an isthmus, 

 and situated on the windpipe in the neck, and is larger in 

 the female than the male. It is exceedingly vascular, and 

 consists of numbers of minute vesicles, with glairy contents, 

 and each invested with a rich network of capillaries. It is 

 sometimes subject to enormous enlargement, constituting the 

 disease called goitre, a tumour remarkable not merely for 

 the great size which it sometimes acquires, but for being 

 associated frequently with a form of idiocy and general 

 deficiency of development, to which the name of cretinism is 

 given. But nothing precise is known of the function of the 

 thyroid body. 



The thymus gland is a structure situated lower down on 

 the windpipe than the thyroid, being placed in the upper 



