28 MANUAL OF HISTOLOGY. 



concentrated watery solution, dilute it with six times its 

 volume of water, then immerse the preparations from 5 to 20 

 minutes, wash them out and clarify in oil of cloves or glycerine. 

 The peculiarity of this material is that it never affects the 

 nucleus, but only the cell-body. More frequently, however, it 

 is the intercellular substance that is colored blue. 



Purpurine. Ranvier has recommended this dye, which is 

 extracted from madder. Alum (one part) is dissolved in dis- 

 tilled water (two hundred parts) ; the fluid is then heated to 

 the boiling point in a porcelain dish. Thea a small quantity 

 of purpurine is dissolved in distilled water and added to it. 

 Sufficient purpurine should be added to leave a residue, by 

 which it is certain that the solution is saturated. While still 

 hot it is to be filtered into alcohol of one-fourth the total 

 volume. The fluid has an orange red color, and is more effi- 

 cient when fresh. Sections should be immersed from 24 to 48 

 hours. 



Frencli arcJiil Staining with extract. Wedl uses this 

 substance, which, after the loss of the ammonia, is dissolved 

 in 20 c.c. absolute alcohol, 5 c.c. acetic acid of 1.070 sp. gr., 

 and40c.c. of distilled water so as to make a saturated solu- 

 tion. Protoplasm and matrix, but not nuclei, are colored a 

 beautiful red. 



Alizarine. This aniline color is recommended by Than- 

 hoffer, but experience is limited with reference to it. It has a 

 golden yellow color, and is easily fixed by the tissues. 



METALLIC SOLUTIONS. 



Staining with osmic and oxalic acids. Broesicke adopts 

 the following method : 



Little pieces of fresh or freshly dried preparations are left 

 for an hour in a one per cent, solution of osmic acid ; then 

 they are carefully washed and soaked in a cold saturated solu- 

 tion of oxalic acid, and finally examined in water or gly- 

 cerine. Elastic fibres are yellow, fat is black, while the walls 

 of capillaries and many connective- tissue substances are 

 red. 



Chloride of gold and lemon juice. Ranvier is in the 

 habit of demonstrating the corneal nerves by using lemon- 



