THE MOUTH AND ITS GLANDS. 



207 



Epithelium. 



Closed 

 follicle. 



Mucous 

 gland. 



Fig. 151. 

 Section of a mucous follicle from the tongue. 



form a kind of capsule for each follicle. Similar follicles occur in the intestine as solitary- 

 follicles ; in the small intestine they are collected together into Peyer's patches, and in the 

 spleen they occur as Malpighian corpuscles. On the dorsum of the tongue several of these 

 follicles form a slightly oval elevation, which is surrounded by connective-tissue. In the 

 centre of this elevation there is a depression, 

 into which a mucous gland opens, which fills 

 the small crater with mucus (fig. 151). 



The tonsils have fundamentally the same 

 structure. On their surface are a number of 

 depressions into which the ducts of small 

 mucous glands open. These depressions are 

 surrounded by groups (10-20) of lymph- 

 follicles, and the whole is environed by a 

 capsule of connective-tissue (fig. 152). Large 

 lymph-spaces, communicating with lym- 

 phatics, occur in the neighbourhood of the 

 tonsils, but as yet a direct connection between 

 the spaces in the follicles and the lymph- 

 vessels has not been proved to exist. Similar 

 structures occur in the tubal and pharyngeal 

 tonsils. [Stohr asserts that an enormous num- 

 ber of leucocytes wander out of the tonsils, 

 solitary and Peyer's glands, and the adenoid 

 tissue of the bronchial mucous membrane. 

 The cells pass out between the epithelial cells, 

 but do not pass into the interior of the latter. ] 



Nerves. Numerous medullated nerve-fibres occur in the sub-mucosa, pass into the mucosa, 

 and terminate partly in the individual papillse in Krause's end-bulbs, which are most abundant 

 in -the lips and soft palate, and not so numerous in the cheeks and floor of the mouth. The 

 nerves administer not only to common sensation, but they are also the organs of transmissions 



for tactile (heat and pressure) . . ^^ 



impressions. It is highly . "~~~ ~-^ 



probable, however, that some 

 nerve-fibres end in fine ter- 

 minal fibrils, between the 

 epithelial cells, as in the 

 cornea and elsewhere. 



[Secretory glands may be 

 simple (fig. 153, B, C, D) or 

 compound ( E) . In the latter 

 case the duct is branched. 

 In the process of develop- 

 ment, a solid process of the 

 -epithelium sinks into the 

 subjacent fibrous tissue, and, 

 to form a simple gland, a 

 cavity appears in this bud, 

 but for a compound gland, 

 other epithelial buds sprout J1- 

 from its blind end. Each 

 bud acquires a central cavity, 

 these elongate and increase 

 in number, thus forming a 

 much branched system, the j^ g -^2 



terminal blind ends forming Tr ,.,/.- < . ., ' , ' .-. n ..*. v > 



the acini alveoH or true Vertical section of a human tonsil, x 20. 1, cavity ; 2, epithelium 

 secretory part. If the alveoli infiltrated with leucocytes below and on the left, but free on the 

 are tubular in shape, the 

 gland is called a compound 

 tubular gland. Thus in the compound glands some parts are secretory, and others act as ducts, 

 While in the simple glands, all the parts may be secretory. All the glands opening on the surface 

 of the body are of epiblastic origin. The secretory cells lining the acini rest on a basement 

 membrane, and outside this are the lymph-spaces and capillary blood-vessels.] 



! 142. THE SALIVABY GLANDS. The three pairs of salivary glands, sub-maxillary, sub- 

 lingual, and parotid, are compound tubular glands. Fig. 155, A, shows a fine duct, terminating 

 in the more or less flask-shaped alveoli or acini.. - [Each gland consists of a number of lobes,, and 



mm, 



Epithelium. 



right ; 3, adenoid tissue with sections a, b, c, of masses of it ; 

 4, fibrous sheath ; 5, section of a gland-duct ; d, blood-vessel. 



