GLANDS. 



recognised in them radicles of lymphatics. No exter- 

 nal outlet has been discovered, after the most rigor- 

 ous examination of the external surfaces of these 

 glands. Reasoning from the structure of these 

 organs, and also from certain pathological relations 

 existing between them and the mesenteric glands, the 

 conclusion seems to us legitimate that they are iden- 

 tical in their nature with lymphatic glands. This 

 opinion is sustained, also, by the most distinguished 

 histologists of Germany. These ductless glands are 

 what are known as the solitary glands of the intes- 

 tine ; they constitute the essential portion of Peyer's 

 glands, of the tonsils, the follicles of the tongue, and 

 the pharynx. The structure of the vesicles of the 

 thymus gland warrants us also in including it in the 

 same category. 



Thyroid body. The fibrous envelop of the thyroid Thyroid body 

 body gives off from its internal surface a great num- 

 ber of delicate trabeculse of connecting tissue by which 

 its interior is divided up into spaces, or cavities, in 

 which the vesicles, of the gland are contained (PL 

 XXII. fig. VIII.) . Each vesicle is thus enclosed by 

 a delicate partition of connective fibres, in the sub- 

 stance of which a considerable number of plasmatic 

 cells are found, together with an abundance of ves- 

 sels (fig. VIII. 2, 3). A single layer of polygonal 

 epithelium lines the interior of the vesicle, and its 

 cavity is filled with an albuminous fluid. In the 

 foetus, and young child, the epithelial layer consists 

 of cells Troth of a line in diameter, with finely granu- 

 lar contents, and a nucleus measuring about zieth of 

 a line. But in the adult, and in old age, it is very 



9 



