SPECIAL ANATOMY. 39 



c. Perspiratory glands, organa sudoripara, consist of a blind tube, which, 

 reaches downwards deeply into the cutis as far as the layer of fat (where it 

 is convoluted), and opens with a spiral excretory duct, which is lined with 

 pavement epithelium, like a funnel upon the surface of the skin. Their 

 openings (pores) are placed in the grooves between the Papillae. [On the 

 ridges. THAWS.] They secrete a fluid filled with mucous corpuscles and epi- 

 dermis scales. Similar in structure are the Ceruminous glands of the ear, the 

 cells and contents of which, however, are different ; their secretion contains 

 fat vesicles. 



40. II. Mucous membrane, Membrana mucosa. 



It lines the internal cavities, since it penetrates, as the immediate 

 continuation of the Cutis, at the external openings into the in- 

 terior, passes through the whole digestive canal, and covers the 

 respiratory organs, glands, urinary and genital organs. It is soft, 

 like velvet, plentifully supplied with vessels and nerves, thicker 

 or thinner, according to situation, greyish white or red, and par- 

 ticularly strongly developed at the external openings. It consists, 

 like the Cutis, of Epithelium and a peculiar membrane of uniting 

 tissue, which is connected to a muscular layer by more or less 

 strongly developed uniting tissue (tunica nervea). One or more 

 of these layers are lost as they proceed. The epithelium is thin- 

 ner and more slimy (as the so-called rete Malpighii occupies the 

 surface), the uniting tissue is more delicate, e. g.,in the intestines, 

 unites with the fibrous periosteum, where the mucous membrane 

 lies upon bones (when the muscular layer is lost) ; or is remarka- 

 ble for elastic fibres in the Trachaea and the Bronchi. 



Like the external skin, it is beset with projections (folds, valves, 

 villi, and papillae) and depressions (sulci and fossa?). 



a. The folds are for the purpose of increasing the superficies in the interior 

 of canals and cavities, where absorption, secretion, or sensation is the object ; 

 and may, after removing the muscular coat, be drawn out {plicae. Kerkring. in 

 the intestines, columna rugarwn in the Vagina, &c.). 



b. The papillae are also present, especially in places which are designedly 

 very sensitive to touch, e. g., the lips, gums, tongue, palate, labia externa, 

 vagina. 



c. The villi are present upon the mucous membrane of the small intestines 

 only; they resemble the filamentous papillae, but contain (instead of vascular 

 and nervous loops), lymphatic rete, which have vascular rete spun all round 

 them. 



d. The fossae are the openings of the mucous glandules, folliculi mucosi. 

 The simple mucous glandules are not always closed follicles (gl. solitaria and 

 Peyeriance), over which the mucous membrane, with its villi, passes. When 

 open, they appear to be inversions of the mucous membrane. To the class of 

 glands with blind sacs belong the dispersed gl. solitarite, the amassed gl. Pey- 

 eriaruz, gl. Lieberku-hniana in the small intestines, the closed gl. tartaricee in the 

 gums, and the glands for secreting the gastric juice in the pylorus ; to the 



