286 TECHNIQUE 



Staining With Silver Nitrate.— The mesothelial covering of pieces 

 of fresh mesentery can be stained in bright simhght with a 1 per 

 cent solution of silver nitrate in distilled water as follows. Remove 

 pieces of the fresh mesentery and spread carefully on a glass slide 

 or stiff moist paper, then place in the bottom of a shallow glass dish. 

 Wash in distilled water. Then bathe the pieces of tissue in the 

 silver nitrate solution for about five minutes. Wash all free silver 

 nitrate away with water and place the tissue in the water in brilliant 

 sunshine until the membrane turns a brown color. If it is desired to 

 stain the nuclei, this can be done by treating with Harris's hema- 

 toxylin. After passing through the various grades of alcohol, 

 aniline oil, xylol, the tissue can be mounted on a slide in balsam. 

 Care should be taken that the tissue does not wrinkle or fold. 



STAINING CELLOIDIN SECTIONS. 



We will suppose that a piece of tissue fixed in Bouin's or Zenker's 

 solution has been embedded in celloidin and that sections of such a 

 piece have been cut with a sliding microtome and collected in a dish 

 in 70 per cent alcohol. We can stain these sections in the Harris 

 hematoxylin and eosin combination as follows: Discard the 70 per 

 cent for 50 per cent alcohol and change this to water, each bath 

 lasting a few minutes. After the sections have been washed in 

 water, the water can be discarded and the dish filled with hematoxy- 

 lin stain. A section can be lifted out occasionally to determine 

 the degree of staining. When the stain has taken sufficiently, it is 

 replaced with water. From this they pass to 50 per cent alcohol; 

 to 70 per cent alcohol; to eosin or orange G for counterstaining ; 

 to 95 per cent alcohol; to aniline oil; to cedar oil or oil of origanum. 

 We merely decant off the liquid in the dish each time and then 

 replace it with the next liquid. At the last step transfer a stained 

 and cleared section to a slide with a spatula and, having added 1 or 

 2 drops of Canada balsam, apply a cover-glass. 



PREPARATION OF STAINS. 



Harris's Hematoxylin.— To prepare this stain make U]) two 

 solutions independently : 



A. Add 1 gram of hematoxylin crystals to 10 cc. of 100 i)er 



cent ethyl alcohol. 



B. Add 20 grams of potassium or aiiimoniuin alum to 200 cc. 



of distilled water. To get the alum into sohitiou it is 

 necessary to heat to boiling. 



