374 CHAPTER XXXI. 



the human subject. But in the case of the lower animals it 

 is possible to introduce fixing liquids into the living nerve- 

 centres by means of injection, thus ensuring a much better 

 penetration of the reagents than can be obtained by simple 

 immersion. 



GOLGI (Arch. Ital. de Biologie, t. vii, 1886, p. 30) injects 

 2*5 per cent, solution of bichromate of potash,, through the 

 carotid if he wishes to limit the hardening to the encephal<-n, 

 or through the aorta if he desires to fix the spinal cord. 



DR QUKRVAIN (Virchon-'s Archir, cxxxiii, 1893, p. 489) 

 injects solution of Miiller warmed to body heat. For dogs 

 300 to 400 c.c. are required, for cats one third to one half 

 that quantity. After injection the whole organ is put into 

 solution of Miiller for some weeks. 



(Further details in fourth edition.) 



MANN (Zeit. wiss. Mile., xi, 1894, p. 482) injects through 

 the aorta. He first injects for about twenty seconds physio- 

 logical salt solution warmed to 39 C. to wash out the capil- 

 laries, then saturated solution of corrosive sublimafte, warmed 

 to 39 C. After five minutes of injection the brain is re- 

 moved and put for twelve hours into the samo sublimate 

 solution, after which it is either put for permanent preserva- 

 tion into 0*1 per cent, solution of sublimate, or is at once 

 passed through alcohol for imbedding in paraffin. 



See also 741 (GEROTA) and STRONG (New York Acad. of 

 Sci., January 13th, 1896; Anat. Anz., xi, 21, 1896, p. 655; 

 Journ. Comp. Neural., xiii, 1903, p. 291) ; and McFAKLAND 

 (Jonrn. A pp. Micr. } ii, 1899, p. 541). 



HARDENING. 



738. Hardening by the Freezing Method. The ether freezing 

 method is to be preferred. The sections should be floated 

 on to water, treated for a minute on the slide with 0*25 per 

 cent, osmic acid solution, and stained or otherwise treated as 

 desired. See 182 and 183. 



For a detailed description of these manipulations see 

 BE VAN LEWIS'S The Human Brain. Also NAGEOTTE, C. R. 

 Soc. Biol.j Ixvii, 1909, p. 542, who finds that if the tissues 

 are soaked for twenty-four hours before cutting in formol of 

 3 per cent, the formation of ice crystals is diminished. 



