Appendix B: Some Standard Reagents and Their Uses 177 



Gram's solution. 



Iodine 1 gram 



Iodide of potassium 2 grams 



Water 300 c.c. 



After staining, the sections are placed in this solution until 

 they are black (2 to 3 minutes) and are then decolorized in abso- 

 lute alcohol until they appear gray. See also 66. 



45. Gold Chloride. The gold chloride method is used chiefly 

 in the study of nerve-fiber terminations, both motor and sensory, 

 although it is sometimes used for the coloration of other tissue 

 elements (capsules of cartilage, etc.). The process is really an 

 impregnation; through the agency of sunlight and of certain 

 reagents (acetic, citric, formic or oxalic acid) the gold is deposited 

 in the tissues in the form of very fine particles. There are numer- 

 ous modifications of the method, one of which is given in chap. ix. 



46. Golgi's Chrome-Silver Method. See chap. ix. 



47. Hemalum (Mayer's). - 



Hematein . 1 gram 



Alcohol, 95 per cent. . 50 c.c. 



Alum 50 grams 



Distilled water 1000 c.c. 



Dissolve the hematein in the alcohol with the aid of heat. 

 Dissolve the alum in the water and slowly add the hematein solu- 

 tion; thoroughly stir the resulting mixture. Filter if there is 

 any residue of solid material, and add a few crystals of thymol to 

 prevent the formation of mold. The stain may be used imme- 

 diately after preparation. It is valuable for staining in bulk, 

 because it does not overstain, especially if diluted one-half with 

 distilled water. Large objects will require at least 24 hours of 

 staining. After staining, tissues are washed in water thoroughly 

 to insure the removal of all alum. If *a purely nuclear stain is 

 desired, 2 per cent, of glacial acetic acid may be added to the 

 hemalum solution. 



Hematoxylin. For general statement see chap. ii. 



48. Hematoxylin, Conklin's Picro-. 



Delafield's hematoxylin 1 part 



Water 4 parts 



Add one drop of Kleinenberg's picro-sulphuric (25) to each 



