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SECRETION. 



divided, according to their function, into secretions and excretions. The secreted fluids 

 may be subdivided into the permanent secretions, which have a more or less mechanical 

 function, and transitory secretions; some of the latter, like mucus, are thrown off in 

 small quantity, without being actually excrementitious ; others, like most of the digestive 

 fluids, are produced intermittently and they rapidly and finally undergo resorption. 



Tabular View of the Secreted Fluids. 



Serous fluids. 



Synovia! fluid. 



Aqueous humor of the eye. 



Secretions Proper. 

 Permanent Fluids. 



Vitreous humor of the eye. 



Fluid of the labyrinth of the internal ear. 



Cephalo rachidian, or subarachnoid fluid. 



Transitory Fluids. 



Mucus, in many varieties. 



Sebaceous matter. 



Cerumen, the waxy secretion of the external me- 



atus. 



Meibomian fluid. 

 Milk and colostrum. 

 Tears. 



Saliva. 



Gastric juice. 



Pancreatic juice. 



Secretion of the glands of Brunner. 



Secretion of the follicles of Lieberkiihn. 



Secretion of the follicles of the large intestine. 



Bile (also an excretion). 



Excretions. 



Perspiration and the secretion of the axillary 

 glands. 



Urine. 



Bile (also a secretion). 



Fluids containing Formed Anatomical Elements. 



Seminal fluid, containing, beside spermatozoids, the secretions of a number of glandular structures. 

 Fluid of the Graafian follicles. 



Physiological Anatomy of the Serous and Synovial Membranes. 



The serous and synovial membranes, which are frequently classed together by anato- 

 mists, present several well-marked points of distinction, both as regards their structure 

 and the products of their secretion. The serous membranes are the arachnoid, pleura, 

 pericardium, peritoneum, and tunica vaginalis testis. The synovial membranes are 

 found around all the movable articulations. They also form elongated sacs enveloping- 

 many of the long tendons, and they exist in various parts of the body in the form of 

 shut sacs, when they are called bursse. 



Serous Membranes. The structure of the serous membranes is very simple. They 

 consist of a dense tissue of fibres, which is frequently quite closely adherent to the sub- 

 jacent parts, covered by a single layer of pavement, or tesselated epithelium. The 

 fibres are mainly of the inelastic variety, arranged in bundles, interlacing each other in 

 the form of a close net-work, and mingled with small, wavy fibres of elastic tissue and 

 numerous blood-vessels. It has not been satisfactorily demonstrated that the serous 

 membranes contain nerves and lymphatics, although the latter are generally quite abun- 

 dant in the subjacent parts, particularly beneath the serous membranes covering the 

 viscera. The capillary blood-vessels are in the form of a close, polygonal net-work, with 

 sharp angles. The epithelium of the serous membranes is pale, regular, with rather 

 large nuclei, and is easily detached after death. These membranes, as a rule, form closed 

 sacs, with their opposing or free surfaces nearly in apposition. The secretion, which is 

 generally very small in quantity, is usually contained in their cavity. The exception to 

 this rule is the arachnoid membrane, the surfaces of which are exactly in apposition, 



