316 APPENDIX 



VI. TREATMENT WITH SILVER NITRATE AND 

 GOLD CHLORIDE. 



SILVER NITRATE. 



Nitrate of silver is chiefly used (1) to make evident the limits 

 of cells especially of flat cells arranged in a single layer, (2) to 

 show cell-spaces and by staining all the elements of a tissue 

 except its cells (negative image). 



Since proteids and sodium chloride give rise to a precipitate 

 with nitrate of silver, these as a rule should be washed away 

 before the tissue is placed in the silver solution. This is perhaps 

 best done with a '75 p.c. solution of sodium sulphate or potassium 

 nitrate. The washing should in all cases be carried out quickly. 

 If distilled water is used it should be applied for a few seconds 

 only, since it causes rapid swelling and disintegration. In some 

 cases good results can be obtained by treating the tissue straight- 

 way with silver nitrate (cp. p. 72, tendon ; p. 108 2, nerve 



To bring out the outlines of superficial epithelioid cells a very 

 brief treatment ^ to 2 minutes with *2 to *5 p.c. solution of 

 nitrate of silver is sufficient. When it is required to bring out 

 such cells on one side of a membrane only, the membrane should 

 be pinned out with hedgehog quills, or stretched between two 

 rings of gutta-percha, and the surface gently brushed with the 

 silver solution. When it is required to show the lymphatics of 

 a tissue which is covered with epithelioid cells, such as the 

 diaphragm, it is best to brush or scrape away the surface cells 

 before or whilst it is placed in nitrate of silver. 



After treatment with silver nitrate the tissue should be 

 washed with distilled water ; it may then be left for 5 minutes 

 in a gentle stream of water from a tap. 



When the excess of nitrate of silver has been washed away 

 the tissue is exposed to sunlight or to light as bright as possible 

 in either (1) water, (2) acetic acid 1 p.c. ; when much white 



