400 CENTBAL NERVOUS SYSTEM. 



The result of this process is not a true stain, but an " appa- 

 rently black reaction/' the tissues appearing black by trans- 

 mitted light, white by reflected light. Grolgi thinks that 

 there is formed in the tissue elements a precipitate of some 

 substance that renders them opaque. The elements acted on 

 are (1) the ganglion- cells, with all their processes and rami- 

 fications of the processes. These are made more evident than 

 by any other process except the bichromate and silver-nitrate 

 process. An advantage of the mercury process is that it 

 demonstrates nuclei; which is not the case with the silver 

 process. (2) Connective-tissue corpuscles in their charac- 

 teristic radiate form. But the reaction in this case is far 

 less precise and complete than that obtained by the silver 

 process. (3) The blood-vessels, and particularly their mus- 

 cular fibre cells. 



The method gives good results only with the cortex of the 

 cerebral convolutions, hardly any results at all with the 

 spinal cord, and very scanty results with the cerebellum. 

 And, on the whole, the method shows nothing more than 

 can be demonstrated by the silver-nitrate method, but it is 

 superior to it as regards two points : the reaction can always 

 be obtained with perfect certainty in a certain time, and 

 the preparations can be perfectly preserved by the usual 

 methods. 



j TAL (Gazz. degli Ospitali, 1886, No. 68) finds that if sections made by 

 this process be treated with solution of sodium sulphide, a much darker 

 stain is obtained. Sections may then advantageously be double-stained with 

 Magdala red. 



Grolgi's method may be combined with Weigert's nerve stain (see PAL, 

 Wien. med. Jahrb., 1886 ; Zeit.f. wiss. Mik., v, 1, 1887, p. 93). 



761. Cox (Arch. f. mik. Anat., xxxvii, 1891, p. 16 ; Journ. Roy. Mie. 

 Soc., 1891, p. 420) finds the sublimate and bichromate may be used together, 

 and give a uniform impregnation. He used a fluid consisting of 20 parts 

 5 per cent, bichromate, 20 parts 5 per cent, sublimate, 16 parts 5 per cent, 

 simple chromate of potash, and 30 to 40 parts of water. The mixture 

 should be as little acid as possible. The duration of the impregnation is 

 from two to three months. There is considerable difficulty in preserving 

 sections, which must be made with a freezing microtome, alcohol being 

 avoided, treated with solution of sodium carbonate, and mounted without a 

 cover. 



762. MAGINI (Boll Accad. Med. di Roma, 1886 ; Zeit. f. wiss. Mik., 

 1888, p. 87) recommends a development of Grolgi's process in which zinc 

 chloride is used in place of sublimate. Portions of tissue of 2 to 3 cm. cube 



