NEUROLOGICAL METHODS. 421 



753. Acetic Aldehyde. VASSAL K and DONAGGIO (Monitor e 

 Zool., Ital., vi, 1895, p. 82) harden pieces of at most 1 cm. 

 in thickness for fifteen to twenty days in a mixture of five 

 parts of aldehyde with 100 of 3 to 4 per cent, bichromate, 

 changing the fluid after a few days, as soon as it has 

 become dark. The rest as Golgi. 



754. Hardening by Injection. This was recommended by 

 GOLGI, see 744 and 681. He found, however, that the 

 bichromate caused such an energetic contraction of the 

 arterioles that the injection did not penetrate into the 

 capillaries. TOOTH got over this by adding morphia to the 

 injection. 



HILL (op. cit., 747) gets over it by injecting 'through 

 the aorta, whilst the heart is still beating, a solution of 

 bichromate containing 1 per cent, of lactic acid. 



For nitrite of amyl as a vaso-dilator, see 476. 



755. Reviving Over-hardened Tissues. Tissues that have 

 been too long (three to four weeks) in the osmium-bichromate 

 mixture will no longer take on the silver impregnation, as 

 has been explained above. They can, however, be re- 

 vivified and made to impregnate in the following manner, 

 due to GOLGI, and published by SACEBDOTTI (Intern. 

 Monatsschr., xi, 1894, 6, p. 326 ; Zeit. f. wiss. Mik., xi, 3, 

 1894, p. 389). They are washed in a half-saturated solution 

 of acetate of copper until they no longer give a precipitate, 

 and are then put back again for five or six days into the 

 osmium-bichromate mixture. Sections of the impregnated 

 material give remarkably fine images, and will bear mount- 

 ing in thickened oil of cedar under a cover. 



756. Modifications of the Silver Impregnation. KOLOSSOW (Arch, 

 f. mik. Anat., xlix, 1897, p. 592) (after hardening in osmio-bichromate 

 solution) impregnates for two or three days in a 2 to a 3 per cent, solution 

 of silver nitrate in % to per cent, osmic acid solution, and states he thus 

 obtains a more complete impregnation. 



Similarly JUSCHTSCHENKO, see Zeit.f. wiss. Mik., xiv, 1897, p. 82. 



BEBKELEY (Johns Hopkins Hosp. Rep., vi, 1897, p. 1 ; Journ. Roy. Mic. 

 Soc., 1898, p. 242) impregnates, after hardening in the osmio-bichromate, 

 in a freshly prepared solution of two drops of 10 per cent, phospho- 

 molybdic acid to 60 c.c. of 1 per cent, silver nitrate, which in winter 

 should be kept at a temperature of about 25 C. 



