426 SUMMARY OF CURRENT RESEARCHES RELATING TO 



is placed for three months in not less than one litre of saturated 

 solution of bichromate of potash, and the liquid changed twice ; the 

 bichromate is then carefully washed out with water, and the speci- 

 men finally stained entire in one litre of a weakly ammoniacal 

 solution of carminate of ammonia, and may then be prepared for 

 cutting sections by imbedding in gum-glycerine in the usual way. 

 The motor nerves are darkly stained, and the sensory nerves 

 faintly so. 



Preparing Nerve-fibrils of the Brain-* —For making preparations 

 to show the nerve-fibrils of the brain, J. Stilling calls renewed atten- 

 tion to Von Eecklinghausen's method of macerating well-hardened 

 specimens in wood-vinegar. 



CocMneal Carmine-solution.t — J. Czokor grinds to a fine powder 

 7 grammes of cochineal (the same amount whatever quality is used) 

 "with as much burnt alum, and mixes it with 700 grammes distilled 

 ■water and boils it down to 400 grammes. After cooling, a trace of 

 carbolic acid solution is added and the whole filtered. From time to 

 time a little carbolic acid solution must be added, and the solution 

 filtered again. It stains substances prepared with alcohol or with 

 chromic acid, the latter rather more slowly than the former. A 

 solution made with a better quality of cochineal stains the nuclei 

 the same colour as hfematoxylin, the other tissues in various shades 

 of red ; if it is prepared with " Blut "-cochineal the intermediate tissue 

 is less deeply coloured, the action resembling that of Grenacher's 

 carmine. 



Polarized Light as an Addition to Staining,; — Mr. A. D. Michael, 

 describing a plan of which he and Dr. J. Matthews are joint authors, 

 suggests that polarized light might be of use as an addition to staining 

 for vegetable and some animal substances, as it seemed to differentiate 

 tissues somewhat in the same way. In practice it might be found to 

 have its disadvantages, but it might have its advantages. Xo special 

 preparation of the tissues was required, and the conditions were more 

 natural than if they had undergone the process of bleaching and 

 staining. It would also be possible, when they had a known selenite, 

 always to repeat the same effect when required, whereas stained 

 tissues frequently fade, and if there were any doubt as to the meaning 

 of what was seen, the effects could be altered, and results secured that 

 would be unattainable with the fixed effects of double staining. There 

 was, of course, no difficulty in getting triple staining, or producing 

 various colours, but the object which he showed was as if stained 

 with a single colour only. [It was a section of Serjanus shown 

 with oblique polarized light on a black ground.] He had heard some 

 discussion as to the best means of obtaining polarized light on a 

 black ground, and had heard it suggested that the results depended 

 entirely on the object, that it was to be obtained only now and then 



* Arch. Mikr. Anat., xviii. (3 880) p. 468. 



t Arch. Mikr. Anat., xviii. (1»80) pp. 412-14. Cf. Zool. Jahresber. Neapel for 

 1880, i. p. i2. 



X Joiim. Quek. Micr. Club, i. (1882) pp. 49-51. 



