138 GLANDS. 



difficult to find the epithelium well marked and dis- 

 tinctly separate from the liquid contents of the vesi- 

 cle; most frequently its cells are found infiltrated 

 with fat, and a large number of free oil globules and 

 nuclei are contained in the liquid which fills the vesi- 

 cle, which is evidence of the disintegration and break- 

 ing down of its elements (fig. VIII. 4). It is doubtless 

 in these vesicles, or follicles, of the thyroid, that most 

 of the morbid growths to which the gland is liable, 

 take their origin. The lobulated shape of the thyroid 

 body depends upon the aggregation of its follicles 

 into little masses, or lobules, which remain to a cer- 

 tain extent independent of each other. 

 vessels. The blood-vessels of the thyroid are remarkable 

 for their size and number, and the rich and delicate 

 plexuses of capillaries which they form around the 

 walls of each follicle. Its nerves come from the 

 sympathetic ; with regard to their mode of termina- 

 tion, as well as to the distribution of its lymphatics, 

 nothing is certainly known. 



Development. The facts ascertained thus far in relation to the 

 development of the thyroid gland are not sufficiently 

 accurate and positive to justify their record in this 

 work. 



spleen. Spleen. The spleen is an organ in regard to the 

 structure of which much remains yet to be elucidated ; 

 the following account includes all that the labors of 

 the most eminent microscopic anatomists have thus 

 far established as certain. 



The envelop of this vascular gland is similar to 

 that of the liver, and is intimately adherent, exter- 

 nally, to the peritonaeum, and internally, to its paren- 



