426 ClIAPTBIi XXXI V. 



Soc. Biol. [10], i, 1894, p. 839) ; and Kalliits {Eiicyd. mih. Technik., 

 Art. " Golgi'sclie Methode.'' 



Modijicatioiis concerning the Iiiipregncdion of the Tissues. 



814. Ramon y Oajal {Zeit. nl-^s. Mih., vii, 1890, p. 332) gives 

 3 per cent, as the strength of the bichromate in the mixture 

 for the rapid process, and in numerous other places has 

 given it as 3'5 per cent. This latter strength has been 

 adopted by most of the workers who use the rapid process, 

 and the mixture containing this proportion of bichromate is 

 generally known as Ramon y Oajal's mixture. 



815. Ramon y Oajal's Double-Impregnation Process (Trab. 

 Lab. Hist. Med. Barcelona, 1891 ; La Cellule, vii, 1891, p. 

 130). — Sometimes the usual rapid method fails to give good 

 impregnations. These, however, may frequently be obtained 

 by putting the tissues back for a day or two into the osmium- 

 bichromate mixture, or into a weaker one containing only 

 two parts of osmic acid solution to 20 of the bichromate. 

 After this they are washed quickly with distilled water, and 

 put for a second time into the silver solution for thirty-six to 

 forty-eight hours. It is important to hit off the proper 

 duration of the first impregnation in the bichromate. If it 

 has been too long (four days) or too short (one day), the 

 second impregnation will not succeed. In this case a third 

 impregnation must be resorted to, the objects being again 

 treated with the weak osmium-bichromate mixture, and after- 

 wards again with the silver solution. 



This modification of the original process is the most impor- 

 tant that has hitherto been made. 



816. GoLGi's Process for Rejuvenation of Over-hardened 

 Tissues. — Tissues that have been much too long in the osmium- 

 bichromate mixture will no longer take on the silver impregna- 

 tion. They can, however, be rejuvenated and made to 

 impregnate in the following manner, due to Golgi, and 

 published by Sacerdotti {Intern. Monatssclir., xi, 1894, p. 

 326). 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, it is said, will bear 

 mounting in thickened oil of cedar under a cover. 



