LYMPH CHANNELS. 163 



PRACTICAL DEMONSTKATION. 



LYMPHATIC VESSELS OF THE CENTRAL TENDON" OF THE DIAPHRAGM. 



(Figs. 110 and 111.) 



This demonstration had best be made with tissue from the rabbit, 

 inasmuch as the slightest decomposition of the epithelium would be 

 fatal to success. 



A small (preferably white) rabbit should be quickly killed by de- 

 capitation, and immediately suspended by the hind legs, so as to 

 thoroughly drain the body of blood. As soon as the blood has ceased 

 dripping, open the thoracic cavity by slitting up the skin along the 

 median line, pushing it to the sides and removing the sternum. In 

 this operation, work rapidly and avoid soiling the internal parts. 

 Then with the fingers of one hand raise the lungs and heart from the 

 diaphragm, and with a large camel's-hair brush proceed to quickly, 

 and quite forcibly, pencil the white glistening surface of the central 

 diaphragmatic tendon, moistening the brush from time to time in the 

 lymph of the pleural cavity. Should the quantity of fluid be small, 

 add a little distilled or previously boiled and filtered water. The 

 object of the brushing is to remove the epithelial cells which cover 

 the surface, and which would otherwise hide the lymph spaces. After 

 the pencilling, drain away the fluid, and pour over the brushed sur- 

 face a solution of one grain of nitrate of silver to an ounce of distilled 

 water.* Allow the silver solution to remain for twenty minutes in 

 contact with the tissue, the body meanwhile being kept away from 

 the bright sunlight; then pour off the solution, wash the surface 

 twice with distilled water, and afterwards allow water from the tap 

 to flow over the parts for at least five minutes. 



If yon observe the directions carefully, the surface of the tendon 

 will lose its original glistening appearance and become whitish and 

 opaque. 



The tendon, or such portion of it as you wish to preserve, may be 

 cut out with the scissors after the washing, thrown into glycerin, and 

 placed in the sunlight until the surface becomes brown. With the 

 forceps tear off small pieces of the stained side, say one-half inch 

 square, and examine in glycerin, or mount them permanently in the 

 same medium. 



The demonstration of the channels of the lymphatic system is based 

 upon the following: 



1. Lymph channels are always, however small or irregular, lined 

 with flattened cells in a single layer, i. e., pavement endothelium. 



2. The lining cells are cemented together with an albuminous sub- 

 stance. 



* Water which has been well boiled in a clean vessel, and afterward care- 

 fully filtered, may be generally employed in histological work when distilled 

 water is not available. 



