ZOOLOGY AND BOTANY, MICROSCOPY, ETC. ... 4,7 



Methods for Silver Impregnation of Nervous Tissue.* — S. Ramon 

 y Cajal describes the following methods for impregnating nervous tissue 

 with silver. 



1. Method specially adapted for the fibrils of small and medium- 

 sized cells. Pieces of tissue about 3 mm. thick, and as fresh as 

 possible, are immersed in a 0*75 to 3 p.c. solution of silver nitrate in 

 distilled water, and incubated for 3 days at from 30° to 35° C. On 

 removal, the pieces are washed for a minute or two in distilled water, 

 and placed in the following reducing medium for 2-4 hours : Pyrogallic 

 acid or hydrochinon 1 to 2 grm., water 100 grm., formalin 5 grm. 

 The pieces are washed for some minutes in distilled water, hardened in 

 alcohol and imbedded in celloidin. 



2. Method adapted for medullated nerves and the fibrils of the large 

 cells. The pieces of tissue are fixed for 24 hours in 97 p.c. alcohol. 

 After washing in distilled water for a few seconds, the pieces are im- 

 mersed in 1 p.c. silver nitrate solution and incubated at from 30° to 

 35° C. After washing for a few seconds the pieces are placed in a 

 reducing solution composed of hydrochinon 2 grm., water 100 grm., 

 formalin 5 grm. The reduction may be hastened by the addition of 

 0'5 grm. sodium sulphite. The pieces are then washed, dehydrated 

 and imbedded in celloidin. Should the sections from the deeeper parte 

 be insufficiently impregnated they are to be treated with the following 

 gold solution : Ammonium sulphocyanate 3 grm., sodium hyposulphite 

 3 grm., gold chloride 1 p.c. solution (a few drops). The sections are 

 washed, dehydrated, cleared up and mounted in dammar. 



3. Method for staining non-medullated fibres and terminal twigs. 

 The pieces are fixed for 3 days in alcohol, but all the other steps are 

 the same as in the two previous methods. 



4. Staining the fibrils of large cells and of fine nerve-fibres. The 

 pieces of tissue are placed in the following solution : Alcohol 97 p.c. 

 100 c.cm., ammonia 0'5 to 1 c.cm. If the pieces are large or numerous 

 a 1*5 ammoniated alcohol solution may be used, or the immersion may 

 be prolonged up to 2 days. 



The preparations are next washed in water, and then transferred to 

 1 • 5 p.c. silver nitrate solution ; after which they are treated with the 

 reduction fluid previously described. 



The best results were obtained by an immersion of the pieces for 

 24 to 36 hours in the ammoniated alcohol. Should the sections be 

 insufficiently impregnated they may be afterwards treated with the gold 

 chloride solution. Instead of alcohol, ammoniated formalin may be 

 used, e.g. formalin 20 c.cm., water 100 c.cm., ammonia 0'5 c.cm. The 

 pieces must be washed in running water for 24 hours in order to get 

 rid of the formalin before they are placed in the silver nitrate solution. 



Demonstrating a Parasite Found in Cases of Enlarged Spleen. f 



t S. R. Christophers, in a preliminary report on a parasite found in 



persons suffering from enlargement of the spleen in India, employed 



the following method for demonstrating their presence in the tissues. 



* Zeitschr. wiss. Mikr.. xx. (1904) pp. 401-8. 



t Scientific Mem. Med. and San. Departs., Govt.; of India, No. 8 (1904) 17 pp., 

 pll. 



