148 SUMMARY OF CURRENT RESEARCHES RELATING TO 



solution having a blue-violet colour. Strong solutions stain rapidly, and 

 the nuclei are darker than the protoplasm. Alkaline solutions change 

 the blue hue to red, and eventually decolorize the section. Acids, 

 alcohol, and clarifying media do not at all affect the dye. It appears to 

 be a good substitute for hsematoxylin. 



(5) Chrysophenin. A sulphur-yellow pigment, but little soluble in 

 water, easily soluble in alcohol. Preparations stained in an alcoholic 

 solution assume a diffuse yellow colour. It is unaffected by acids and 

 alkalies. 



(6) Ehodanin-red and rhodanin-violet. Both are basic dyes, soluble 

 in water and spirit. The stains imparted by their solution are carmine- 

 red and reddish-violet. The pigment is rapidly extracted both by spirit 

 and water. They stain bacteria, but no mordant has been found to fix 

 them. 



Of the foregoing six pigments, it will be seen that two are very suit- 

 able for histological purposes, viz. benzopurpurin B and benzoazurin. 



Carmine Staining of Nervous Tissue.* — Dr. H. S. Upson gives the 

 three following methods for staining nervous tissue after Miiller's fluid 

 or alcohol. 



(1) The following alum-carmine solution is first made. 1 gram car- 

 mine is boiled with 100 ccm. of a 5 per cent, alum solution (rubidium alum 

 is the best). To 5 ccm. of this solution are added 10-20 drops of acetic 

 acid and 1 to 3 drops of molybdo-phosphoric acid, and then filtered. 

 The sections are placed in this mixture for 2 to 10 minutes, or longer, 

 and then carefully washed, dehydrated, cleared up, and imbedded. The 

 axis-cylinders, ganglion-cells, and connective tissues are stained, and 

 the nuclei very clearly. 



(2) 5 ccm. of the foregoing alum-carmine solution are saturated with 

 zinc sulphate and filtered. Sections are placed in this solution for 

 1/2 to 12 hours, and then treated as above. This method gives very 

 good results, especially with peripheral nerves and spinal cord. 



(3) • 06 grm. carminic acid are dissolved in a mixture of 4 ccm. water 

 and 1 ccm. spirit. The sections remain in the mixture for 8 to 10 minutes, 

 are then washed for a short time in water, and are then placed in one of 

 the following mordants for a few minutes. They are then washed in 

 water and treated as before. The action of the mordants produces the 

 following staining : — Dilute acetic acid, a yellowish-red ; saturated so- 

 lution of lead acetate, blue ; iron sulphate, black ; manganese sulphate, 

 red ; nickel sulphate or barium- chloride, violet. The longer th(? tissue 

 has remained in Miiller's fluid or spirit the more lasting the stain will be. 



Staining" Microbes black for Photomicrography.f — Dr. E. Neuhauss 

 stains bacteria black in the following way. Campeachy wood extract is 

 dissolved in boiling water and the solution filtered as hot as possible. 

 After this has stood for at least eight days it is warmed up every time it 

 is to be used. The cover-glass to be stained is boiled in the solution 

 for ten minutes. It is next washed in hot water and afterwards im- 

 mersed for a long time in a weak solution of neutral chromate of soda. 

 This solution is made by adding, drop by drop, a 5 per cent, soda 

 solution to a weak boiling solution of chromic, and until the liquid 

 gives a neutral reaction. 



* Neurol. Centralbl., vii. (1888) pp. 319-21. Cf. Zeitschr. f. Wiss. Mikr., v. 

 (1888) pp. 525-6. f Zeitschr. f. Wiss. Mikr., v. (1888) pp. 484-6. 



