130 HOW TO WORK 



It has been stated that no method of preserving nerve tissue has 

 been devised which makes it worth while to mount preparations for 

 the sake of displaying its minute characters, and this statement, 

 strange to say, has been repeated in books devoted expressly 

 to mounting objects. It need scarcely be stated here that the most 

 delicate of the nerve textures can be mounted permanently. Not 

 only so, but new facts in connection with their ultimate arrangement 

 can be demonstrated in specimens which have been kept for some 

 time, and fine fibres seen which were quite invisible when mounted. 

 There are in truth very few objects which cannot be preserved per- 

 manently, so as to show far more than can be demonstrated in them 

 as fresh specimens. The use of chromic and acetic acids, and per- 

 chloride of gold in the investigation of nerve structures has been 

 referred to in p. 113. 



Examination of Serous and Mucous Membranes. 



228. Examination of Serous ami Synovia! Membranes. Serous 

 membranes may be examined according to the general directions, 

 previously given. It will sometimes be found difficult to demon- 

 strate the delicate cells upon their surface, and fresh specimens only 

 should be examined. The epithelium of serous membranes, when 

 it exists, is of the pavement or tessellated variety, and appears to form 

 one single layer. 



A small portion of the peritoneum of a mouse or other small 

 animal, will be found to display well the fibres of the sub-basement 

 tissue, and often vessels and nerves may be seen beautifully distinct 

 in this situation. The greater part of the thickness of serous mem- 

 branes is made up of condensed areolar tissue, in which the yellow 

 fibrous element is very abundant. This areolar tissue becomes less 

 dense at a greater distance from the surface, and often -contains fat 

 cells like the subcutaneous areolar tissue. 



In order to examine the distribution of the vessels in synovial 

 membranes, an injected specimen is necessary. The fringe-like pro- 

 cesses which project into many of the joints are highly vascular, 

 and a well-injected specimen forms a beautiful object. The surface 

 in the recent state is covered with large cells of a more or less 

 globular form. 



The vessels which run between synovial membrane and cartilage 

 are very tortuous, and exhibit considerable dilatations and varico- 

 sities. The characters of serous and synovial membranes are fully 

 described in Dr. Brinton's article "Serous and Synovial Membranes," 

 Cyclopsedia of Anatomy and Physiology. 



