138 HUMAN PHYSIOLOGY. 



TRANSITORY FLUIDS. 



Mucus. Gastric juice. 



Sebaceous matter. Pancreatic juice. 



Cerumen (external meatus). Secretion from Brunner's glands. 



Meibomian fluid. Secretion from Lieberkiihn's glands. 



Milk and colostrum.' Secretions from follicles of the large 



Tears. intestine. 



Saliva. Bile (also an excretion). 



EXCRETIONS. 



Perspiration and the secretion of the Urine. 



axillary glands. Bile (also a secretion). 



FLUIDS CONTAINING FORMED ANATOMIC ELEMENTS. 



Seminal fluid, containing spermat- Fluid of the Graafian follicles con- 

 ozoids. taining the ovum. 



The essential apparatus for secretion is a delicate, homogeneous, struc- 

 tureless membrane, on one side of which, in close contact, is a capillary plexus 

 of blood-vessels, and on the other side a layer of cells the physiologic function 

 of which varies in different situations. 



Secreting organs may be divided into membranes and glands. 



Serous membranes usually exist as closed sacs, the inner surfaces of which 

 are covered by pale, nucleated epithelium, containing a small amount of 

 secretion. 



The serous membranes are the pleura, peritoneum, pericardium, synovial 

 sacs, etc. 



The serous fluids are of a pale amber color, somewhat viscid, alkaline, 

 coagulable by heat, and resemble the serum of the blood; their amount is 

 but small. The pleural fluid varies from four to seven drams; the peritoneal 

 from one to four ounces; the pericardial from one to three drams. 



The synovial fluid is colorless, alkaline, and extremely viscid, from the 

 presence of synovin. 



The function of serous fluids is to moisten the opposing surfaces, so as to 

 prevent friction during the play of the viscera. 



The mucous membranes are soft and velvety in character, and line the 

 cavities and passages leading to the exterior of the body e. g., the gastro- 

 intestinal, pulmonary and genito-urinary. They consist of a primary base- 

 ment membrane covered with epithelial cells, which in some situations are 

 tessellated, in others, columnar. 



