226 



PRACTICAL HISTOLOGY. 



[XIX. 



valve in chromic and spirit fluid (two weeks), make transverse 

 sections, stain in logwood, and mount in balsam. Alcohol does 



well as a hardening re- 

 agent, and the sections 

 can then be readily 

 stained in picro-carmine. 



(a.) On the surface, 

 toward the auricle (A), 

 note a superficial layer 

 of lamellated connective 



FIG. 209. Endocardium of Left Ventricle (Human), fjccmp whir-h iq rovprprl 

 a. Superficial layer ; ml. Smooth muscular fibres ; l U6 W 

 tc. Fasciculated fibrous tissue; inc. Muscle of With eildofclielium (ll. 



heart, x 150. 



2IOj 



an j_ underneath 



this a fibrous basis with elastic fibres (re). 



(b.) If the section passes through the insertion of one of the 

 chordae tendinese, it presents the appearance shown in fig. 210, ct. 



5. Aorta. (i.) Make transverse (and longitudinal) sections of 

 the human aorta, or of that of an ox, which has been hardened in 

 alcohol, or, preferably, in 2 per cent, potassic bichromate (ten days). 

 Stain a section in picro-carmine, and mount it in glycerine. 



(ii.) Another good method is to slit up any large artery, pin 



FIG. 210. T.So of the Cusp of the Human Tricuspid Valve, vertical to the axis of the 

 cusp. A. Auricular, B. Ventricular surface; a. Superficial lamellated layer of the 

 auricular, and a', of the ventricular surface; ct. T.S. of one of the chorda; tendineee, 

 where it is inserted into the valve ; re. Fibrous tissue, the basis of the valve, x 100. 



it, inner surface upwards, upon wood. The pins must be close 

 together to prevent too great shrinking of the tissue. Place it in 

 a dry, well-aired place, say near a fire, so that it dries within a few 

 hours. Make transverse sections with a sharp razor. This is best 

 done by making a slit in a cork and clamping the dried membrane 

 in the slit. Place the sections in water; they swell up greatly. 



Remove them, 

 glycerine. 



stain with picro-carmine, and mount in formic 



