Impregnation of Tissues. 



Silver Nitrate. 



This is used for staining the endothelial membranes 

 lining blood-vessels and serous cavities. An albumenate of 

 silver is formed with the intercellular cement between the 

 endothelial cells; the silver is reduced on exposing to sun- 

 light. A 1% aqueous solution of the silver nitrate is 

 used. In making a preparation of an endothelial mem- 

 brane, the peritoneum of a frog may be selected. Make a 

 small opening through the abdominal wall of a frog near 

 the sternum, inject 10 to 20 c.c. of the 1% solution of 

 silver nitrate ; while injecting, the abdomen is gently 

 kneaded, so that the fluid may be well distributed in the 

 abdominal cavity. In 15 to 20 minutes the abdomen is 

 opened, the intestinal canal with the mesentery is removed, 

 the latter (without removing from the intestines) is pinned 

 out on a cork board, is now immersed, preparation side up, 

 in 80% alcohol (it will be necessary to fix small lead 

 weights to the cork to bring it under the alcohol), and 

 placed in the sunlight ; as soon as the tissue shows a brown 

 color it is ready for study. It may be mounted in gum 

 glycerine or balsam. 



Another method is to carefully remove the peritoneum, 

 pleura, or pericardial sack, and spread out on a clean, dry 

 slide, to which the tissue will adhere quite firmly if set aside 

 for a few moments. The slide with the tissue on it may 

 then be placed in the silver nitrate solution and treated 

 as above. Connective tissue, .when stained in silver nitrate 

 to show the cell spaces, may be prepared in the same way. 

 If it is desired to mount the tissue in balsam, it may, 



