736 SUMMARY OF CURRENT RESEARCHES RELATING TO 



fixing the pieces in 12 p.c. formalin for several days to months ; (2) 

 sections, 20 /x, made by the freezing method are immersed in 2 p.c. 

 silver nitrate for 12-24 hours ; (3) they are then passed through 

 3 p.c. ammonia for 10-20 seconds or until they assume a yellow tinge ; 



(4) after which they are treated with 20 p.c. formalin for 10 minutes ; 



(5) after passing again through 3 p.c. ammonia, they are dipped in 

 • 5 p.c. silver nitrate for \ minute and (6) then treated with 20 p.c. 

 formalin to reduce the silver ; (7) they are next passed through 3 p.c. 

 ammonia and then washed in 20 p.c. formalin for several minutes ; 

 (8) the next step is to treat the sections with the following solution, 

 which imparts to them a violet hue : gold chloride 1 p.c. 2-3 drops, 

 acetic acid 2-3 drops, distilled water, 10 c.cm. ; (9) they are subse- 

 quently passed through 5 p.c. hyposulphite of soda which dissolves the 

 unreduced silver nitrate ; (10) after washing in distilled water and then 

 passing through up-graded alcohols, they are treated with carbol-xylol, 

 and finally mounted in balsam. 



In the second method which is intended for impregnation en 

 masse and paraffin sections, pieces less than 1 cm. thick are fixed in 

 12 p.c. formol and then immersed in 2 p.c. silver nitrate for 24-48 

 hours. After a quick wash in distilled water the pieces are treated for 

 -|-1 hour with an ammoniacal silver solution prepared quite fresh in 

 the following way : 20 c.cm. of 2 p.c. silver nitrate, and 2-3 drops of 

 40 p.c. soda are mixed ; the black precipitate which forms is dissolved 

 by adding ammonia, drop by drop. After washing in water the pieces 

 are treated for 12-24 hours with 20 p.c. formalin, and then comes 

 paraffin imbedding followed by the chloride of gold, and the subsequent 

 stages detailed above. 



The third method consists in fixing pieces less than 1 cm. thick 

 in 10-15 p.c. formalin. Frozen sections 10 /a thick are made, and after 

 being washed in distilled water are immersed for 24 hours in 2 p.c. 

 silver nitrate. After a wash in distilled water the sections are treated 

 for 15 minutes with an ammoniacal silver solution made as above but 

 with 5 c.cm. 10 p.c. silver nitrate. Then follow 20 p.c. formalin, 

 chloride of gold, hyposulphite of soda, etc., as before. 



Method of Staining encapsuled Micro-organisms.* — A. Schadel 

 stains the films for f— 1 minute in ordinary carbol-fuchsin solution and 

 then afterwards for 1 minute in the following solution : mercuric 

 chloride, " 1 grm. ; water and alcohol, 25 c.cm. each. The micro- 

 organisms are stained red, the capsules being colourless against the 

 general pink ground. The stain is permanent. In staining sputa the 

 preparations should be treated with the fuchsin solution for 1£ 

 minutes and for 2 minutes with the mercuric chloride. 



Staining Neuroglia in Ichthyobdella.| — C. Perez and E. Gendre 

 recommend that the material should be fixed in Borrel's chrom-osniic- 

 platinum mixture, and the sections obtained with magenta-red, and then 

 differentiated with picro-indigo-carmin. Some, such as Branchellion, 



* Lancet, 1906, ii. p. 190. 



t Proc. Verb. Soc. Sci. Phys. et Nat, Bordeaux, 1904-5, pp. 50-2. 



