670 APPENDIX. 



cells, or concentric layers of aggregated scales. The distinctions 

 between these growths and true cancer will be pointed out here- 

 after. 



Mucous Membrane. — The submucous areolar tissue maybe exa- 

 mined upon a small piece cut from the under surface of the mu- 

 cous membrane, and torn up with needles. Between the proper 

 muscular coat of the small intestine and the basement-membrane, 

 and in close apposition with the latter, Brucke has demonstrated a 

 thin layer of pale muscular fibres, which is known as the muscu- 

 lar layer of the mucous coat. The contractile fibre-cells of this 

 coat are disposed in circular and longitudinal directions. The 

 villi are best seen in a vertical section of the membrane. By 

 washing ofl"the epithelium, and adding a solution of acetic and 

 nitric acid, composed of about one part of acid to four of water, the 

 muscular fibres of the villi will be brought into view. The villi 

 situated around intestinal ulcers are often found to be very much 

 elongated. In the examination of such ulcers it is important in 

 all cases to ascertain if the muscular coat has suffered from the 

 ulcerative action or not. The presence or absence of non-striated 

 fibres in the base of the ulcer will determine this point. 



Serous and Synovial Membranes. — Serous membranes consist 

 mainly of condensed areolar tissue, containing an abundance of 

 yellow elastic fibres. At the surface this areolar tissue is very 

 dense; the deeper layers are less dense, and often contain fat- 

 cells. Portions of recent membrane are generally necessary to 

 demonstrate the delicate surface-cells. The fibi'es of the sub- 

 basement tissue, and often the vessels and nerves, are well seen 

 in the peritoneum of the mouse and other small animals. The 

 vessels of the synovial membranes should be injected before exa- 

 mination. In an injected specimen, the distribution of the vessels 

 in the fringe-like processes which dip down into the joint, is dis- 

 played to great advantage. In some cases of disease, as in ascites, 

 and pleurisy of long standing, great alterations take place in the 

 structure of the serous membrane, such as the deposition of a 

 thick cellular layer over the whole surface. Cells of a similar 

 character are also found in the fluid contained in the cavity. 



Epithelium. — Epithelium may be obtained for examination by 

 scraping a mucous or serous surface with a sharp knife. It 

 should then be placed upon a slip of glass, and moistened with 

 water. Very delicate cells should be treated with serum, syrup, 

 or a mixture of glycerine and water, in prefei'ence to pure water, 

 as the rapidity of endosmose is checked, and the liability to rup- 

 ture diminished. Acetic and nitric acids, tincture of iodine, and 

 solutions of potash and soda of different strengths, are the most 

 useful reagents in examining epithelium. Various kinds of 

 epithelium are described by histologists. 



Scaly epithelium may be procured from the vagina, the mouth, 

 &c. ; a modified form exists in the epidermis, in nails, and in 

 hair. The vaginal epithelium consists of large, fiat, ragged, and 



