NEUROGLIA AND SENSE ORGANS 559 



mik. Technik., p. 75), who also approves of formol, but insists that it 

 should be acid, and adds 3 to 5 per eent. of acetic acid. 



KoLMKR {Arch. Gesammte PInjs., cxxix, 1909, p. 35), fixes for twelve 

 to twenty-four hours in a mixture of 4 parts saturated solution of 

 bichromate, 4 of formol of 10 per cent., and 1 of acetic acid. 



Benda {Verh. Ges. Naturf. .Erzte, Ixxi, Vers., 1900, p. 459) fixes in 

 nitric acid of 10 per cent., and hardens in liquid of Miiller, twenty-four 

 hours in each. 



ZtJRN (Arch. Anat. Phijs., Anal. Abth., 1902, Supp., p. 106) advises 

 (for mammals) fixing in saturated solution of sublimate in salt solution 

 of 0-6 per cent., with 1 to 1\ per cent, of acetic acid after removing the 

 anterior pole and the vitreous. Wash out in alcohol of 35 per cent, 

 made 5 per cent, stronger each day up to 50 per cent. ; then pass on to 

 stronger and cedar oil and paraffin. 



Zenker's and Bouin's fluids fix the retina excellently. It is 

 usually best first to fix the eye entire, either in one of these solu- 

 tions or in 10 per cent, formol, and after twenty-four hours 

 to open it by a mesial incision after freezing it thoroughly in an 

 ice and salt mixture. When formalin is used the eye should be 

 returned to the fixative for a further twenty-four hours or more. 

 After Zenker's or Bouin's fluid it may be washed at once to clear 

 away the vitreous. 



Greenfield and Nevin {Trans. Ophthal. Soc, liii, 1933, p. 170) 

 recommend for human eyes injecting 1 c.e. of 20 per cent, formalin 

 in saline into the vitreous with a fine hypodermic needle. After 

 six to eight hours the sclerotic may be incised and the eye further 

 fixed in 10 per cent, formalin or Zenker's fluid. 



1102. Staining. For general views w^e recommend iron- 

 hsematoxylin, followed by saurefuchsin or picro-saurefuchsin, 

 or preceded by Bordeaux ; or Kernschwarz, followed by safranin, 

 or the Ehrlich-Biondi stain. 



The Methylen blue intra-vitam stain has given valuable results ; 

 see the methods of Dogiel. 



But the most important method is the bichromate and silver 

 impregnation of Golgi, first applied to this object by Tartuferi 

 {Intern. Monatsschr., iv, 1887, p. 421). This author employed 

 the rapid process. So also Ramon y Cajal {La Cellule, ix, 1893, 

 p. 121) with the double-impregnation process, § 1028, To avoid 

 the formation of precipitates on the tissues, he covers the retina, 

 before silvering, with a piece of peritoneal membrane, or a thin 

 layer of collodion. Or, better, he rolls the retina {op. cit., p. 130). 

 After removing the vitreous, the retina is cut away around the 

 papilla with a punch or fhie scalpel, and separated from the 

 choroid. It is then rolled up (after being cut into quadrants or 

 not), so as to form a solid block. This is painted with 2 per cent, 

 celloidin, which is allowed to dry for a few seconds, and the whole 

 is put into the bichromate mixture, and further treated as a solid 

 mass of tissue. 



Ramon y Cajal also employs his neurofibril silver method, see 



