MODIFICATIONS OF GOLGl's METHOD. 375 



pp. 536, 830 : the Journal here appears to have been track- 

 ing itself in its own snow ; the two reports are literatim iden- 

 tical, the second one being copied from the Amer. Hon. Micr. 

 Journ., 1891, p. 210, which took it verbatim from the Journal's 

 first one) gives the following. Sections of silvered material 

 are made, either without imbedding or after imbedding either 

 in paraffin or celloidin, care being taken in either case not to 

 use alcohol of a lower grade than 94 or 95 per cent. They 

 are brought from absolute alcohol into a mixture of eight to 

 ten drops of 1 per cent, solution of gold chloride with 10 c.c. 

 of absolute alcohol, which should be prepared half an hour 

 beforehand and exposed to diffused light until the sections 

 are placed in it, when it should be put into the dark. After 

 fifteen to thirty minutes therein, according to their thickness, 

 the sections are quickly washed in 50 per cent, alcohol, then 

 in water, then treated for five or ten minutes with 10 per 

 cent, solution of hyposulphite of soda. They are lastly 

 washed well with water, and may then 'be mounted at once 

 in balsam under a cover, or if desired may be previously 

 stained with carmine or hsematoxylin, or Pal's modification of 

 Weigert's process, or the like. 



Obregia thinks that the reason why Sehrwald did not suc- 

 ceed in substituting gold for the silver in his preparations 

 (vide supra) is that he took the gold salt in aqueous solution. 



This method is also applicable to material treated by Grolgi's 

 sublimate process, 760. 



712. FICK (Zeit.f. wiss. Mik., viii, 2, 1891, p. 168) does not 

 admit Samassa's theory of the deterioration of sections through 

 diffusion currents (supra). He points out that bichromate of 

 silver is soluble in water, especially with the aid of heat ; and 

 after an elaborate series of experiments, concludes that the 

 water of the reagents or damp confined by the cover-glass is 

 the cause of the ruin of the preparations. Watery fluids 

 should be avoided, and sections should be mounted without a 

 cover, or on a cover raised free of contact with the slide by 

 means of wax feet, or the like. Or sections mounted without 

 a cover may be later on provided with one if the balsam be 

 first rendered perfectly anhydrous by careful heating. 



This last method is also recommended by HUBEE (Anat. 

 Anz., vii, 1892, p. 587; Journ. Roy. Hie. Soc., 1892, p. 707). 



