84 PHYSIOLOGY. 



the fluid pre-existing in the blood, it soaks out by the physical pro- 

 cess of exosmose. 



The exhalations do not require much notice after what has been 

 said of their mode of separation. Under this head are included 

 those from serous and synovial memh'anes^ which are destined to 

 lubricate them ; the fluid of the areolar tissue, giving softness and 

 suppleness to that tissue ; the watery exhalations from the skin and 

 mucous membranes, a mere physical evaporation ; and the exhala- 

 tion of the aqueous and vitreous humours of the eye, two of its 

 transmitting and refracting media. 



The follicular secretions are divided into two classes, the mucous 

 and cutaneous. In the first division, besides the ordinary follicles 

 which secrete the lubricating mucus, and which are seen generally 

 existing in mucous membranes, there are included the numerous 

 glandulse of the intestinal canal. In the stomach are the simple and 

 compound gastric follicles, opening into little pits or depressions in 

 the mucous membrane ; these follicles secrete the gastric juice. In 

 the duodenum are the glands of Brunner, seated in the suh-m,ucous 

 tissue ; these consist of numerous minute lobules, with a common 

 excretory duct. The nature of their secretion is unknown. In the 

 jejunum, and more particularly in the ilium, are the agminated 

 glands of Payer, which consist of a cavity covered over with an 

 extremely thin membrane, and having no excretory duct ; their 

 secretion probably escapes through the medium of cells developed 

 in this membrane. These glands or follicles are supposed to secrete 

 the putrescent elements of the fseces. Throughout the whole intes- 

 tinal tract, especially in the small intestines, are found the follicles 

 of Lieberkiihn, which secrete the thick, tenacious mucus to lubricate 

 these parts. In the ccecum and lower part of the rectum, are a 

 number of simple and large follicles, producing slight elevations on 

 the surface of the mucous membrane. These are always most 

 abundant where most mucus is required. The glands of Duvergny 

 and Nabothi, in the vagina and cervix uteri are also lubricating 

 mucous follicles: as are also the glands of Cowper, and the prostate 

 in the male. The tonsil glands are considered by some anatomists 

 and physiologists as composed of numerous mucous follicles having 

 the same function, viz., to lubricate the parts on which they are placed. 



The cutaneous follicular secretions include the meibomian, ceru- 

 minous, sebaceous, and sudoriferous. The m£ibomia?i follicles are 

 seated in the substance of the tarsal cartilage, and secrete a gummy 

 fluid to lubricate the edges of the lids. The ceruminous, are seated 

 beneath the skin of the auditory meatus, and consist of a tube con- 

 voluted upon itself. They secrete a resinous substance, nearly solid, 

 and intended to lubricate the external meatus. The sebaceous matter 

 of the skin is secreted by innumerable minute, branched follicles 

 opening by a narrow orifice. These sebaceous glands generally 

 open into the follicles of the hairs. By these an adipose secretion 



