GLANDS. 1131 



glossus muscle, to the upper deep cervical lymph glands, especially to some glands near the 

 bifurcation of the common carotid artery. From the posterior part of the tongue the lymph- 

 vessels pass laterally on each side" below the palatine tonsil, and thence follow the course of the 

 tonsillar lymph -vessels to the upper deep cervical lymph glands. Some central vessels, from 

 the median portion^ of the tongue, pass downwards to the submaxillary glands, and also to the 

 upper deep cervical glands, on the lateral side of the internal jugular vein. 



Nerves. The nerves which supply the tongue are : (1) The hypoglossal nerve, the motor 

 nerve of the tongue, which enters the genioglossus and passes up in its substance to the intrinsic 

 muscles, in which it ends. (2) The lingual nerve, a branch of the mandibular nerve, which is 

 accompanied by the chorda tympani branch of the facial nerve. The lingual, after crossing the 

 hyoglossus, breaks up and enters the longitudinalis inferior and genioglossus muscles, and thus 

 makes its way upwards to the mucous membrane of the anterior two-thirds of the tongue the 

 lingual itself conferring common sensation on this part, the chorda tympani probably carrying to 

 it taste fibres. (3) The glosso-pharyngeal nerve passes forwards beneath the upper part of the 

 hyoglossus muscle, and sends its terminal branches to the mucous membrane of the posterior third 

 of the tongue, supplying the papillae vallatae, and the part of the tongue behind these, with 

 both gustatory and common sensory fibres. (4) Th,e internal laryngeal nerve also distributes a 

 few fibres to the posterior part of the base of the tongue, near the epiglottis. 





GLANDULE. 



Numerous organs, differing widely in structure, function, and development, are 

 commonly included under the term glands. It may indicate any of the following 

 structures : 



(1) Glands producing a visible fluid or semi-fluid secretion, which is dis- 

 charged from the cells of the gland, either directly or by a duct, on to a free 

 surface, where it is useful chemically or mechanically, or by which it is drained 

 away. Glands of this type connected with the alimentary canal are serous and 

 mucous glands, salivary glands, gastric and intestinal glands, and the liver and 

 pancreas. 



(2) The so-called ductless glands, which possess no ducts, but secrete some 

 substances, which are directly and gradually transmitted from the cells of the 

 gland to the blood or lymph stream, and are of use in the general metabolism of the 

 body. Such structures are the thyreoid gland, the suprarenal glands, the para- 

 thyreoids, and the hypophysis cerebri. 



(3) Cytogenic or cell -producing glands, not always epithelial, and usually 

 with no distinct duct, consist of aggregations of special cells, enclosed in a more 

 or less definite framework of connective tissue, freely supplied with blood- and 

 lymph- vessels. Glands of this type are concerned in the production, from the cells 

 in the glands, of special cells, which are liberated - from the gland tissue, and pass 

 away from it. Such glands are lymph glands, the bone marrow, and the repro- 

 ductive glands testes and ovaries. 



In structure they present wide differences. 



Glands may also be classified according to their development, and on this basis 

 the following groups are recognised : 



(1) Glandulse epitheliales, developed from epithelial cells. These may (a) possess 

 a duct, in which case they are termed glandulse evehentes ; or (6) they may be 

 constituted as ductless glands, and they are then termed glandulse clausse. To 

 this last group belong the thyreoid gland, the hypophysis, and the suprarenal 

 glands. 



(2) Glandulse vasculares, developed in connexion with vessels, and not containing 

 epithelial cells. This group includes all the lymph glands, the lymph nodules 

 found in the intestine, the tonsils, the thymus, and the spleen. 



In the following paragraphs only the true glands of the alimentary system 

 namely, the glands of epithelial origin, characterised by the possession of ducts 

 are considered. 



Such glands may be defined as epithelial organs used for the secretion 

 or excretion of some particular substance or substances from the body. They 

 usually consist of a number of cells, and there may be different kinds of cells in a 

 gland. 



