894 SUMMARY OF CURRENT RESEARCHES RELATING TO 



cell-substance is coloured violet. The best results are obtained from 

 solutions of chromo-formic acid and platinum chloride. Formula for 

 cbromo-formic acid : — 1/2 per cent, solution chromic acid, 200 grm. ; 

 concentrated formic acid, 4-5 drops. The mixture is always to be 

 freshly prepared for use. Small pieces of fresh specimens are to be 

 used. After 12 to 24 hours, wash in water and then transfer to 

 60 or 70 per cent, alcohol, and after 24 or 36 hours more to absolute 

 alcohol. A 1/3 per cent, solution platinum chloride has the same 

 effect as gold chloride, and this without being reduced by light or 

 heat. Specimens should remain in this solution 24 hours, they are 

 then washed and treated as before. The one method supplements the 

 other, as chromo-formic acid causes certain fibres to swell, while 

 platinum chloride has a somewhat shrivelling effect. 



Method for showing the Distribution and Termination of Nerves 

 in the Human Lungs.* — Dr. E. F. Beckwith, aware of the futility of 

 hoping to obtain good results from any known manner of preparation 

 and staining of the nerves of the lungs, sought a nev7 method, and 

 the following modification of a process lately promulgated in Germany 

 for staining brain-tissues was found to answer. 



Harden fresh lung for about ten days in the following solution : — 

 Bichromate of potash 2 • 5 per cent., to which is added sulphate of 

 copper C. P. to the amount of • 5 per cent. The tissue is then 

 frozen and suitable sections made, which are treated with gold 

 chloride 0'5 per cent., 2-10 minutes in the dark. Washed with 

 distilled water. Sodium hydrate 1-5, until cleared up. Potassium 

 carbonate 10 per cent., 30-60 minutes. Dried with absorbent paper. 

 Potassium iodide 10 per cent., 15 minutes, when gold will be nicely 

 reduced. 



The nerves and ganglia in sections thus prepared are of a deep 

 red or violet colour, occasionally shading off into a blueish green, the 

 other tissue being red. The differentiation in colour is sharp, so that 

 nerve-tissue may be recognized by its colour alone whenever seen. 



The above method differs very little from the German process, 

 with the exception of the potassium carbonate, which the author 

 believes essential to success, as the unmodified process failed to give 

 good results, when used on lung tissue. A great advantage of the 

 method consists in the fact that the reduction of gold always takes 

 place in a uniformly even manner ; and with little practice, perfect 

 staining can be accomplished with every section. Unfortunately, as 

 in other gold preparations, the specimens spoil in a short time unless 

 preserved in the dark in 40 per cent, alcohol, and when examined 

 should be temporarily mounted in glycerin. 



Preparing Tail of Puppy.f — Mr. A. C. Cole's method of prepara- 

 tion is to first harden the tail in methylated spirit for a week, then 

 soak in water, then place in a considerable quantity of a 1/6 per 

 cent, solution of chromic acid, to every ounce of which five drops of 

 nitric acid are added. This mixture should be frequently changed. 



* The Microscope, v. (18S5) pp. 148-52 (3 fig?.)- 

 t Cole's Studies in Micr. Sci., iii. (1885) Sec. 4, p. 24. 



