NIKIFOROW'S METHOD. 407 



The sections are then washed either in water or alcohol until the grey, 

 matter can be clearly distinguished from the white, are cleared with cedar 

 oil, and mounted in balsam. Nerve-tubes are stained blue, ganglion-cells 

 greenish, nuclei of neuroglia blue. Micrococci are stained, if any be present 

 in the tissues. The preparations are not perfectly permanent. 



774. Safranin followed by methylen blue gives a very special stain of 

 spinal cord. The method is due to ADAMKIEWICS (Sitzb. k. Acad. Wiss. 

 Wien, Math. Naturw. Kl., 1884, p. 245; Zeit. f. wiss. Mik., 1884, p. 587). 

 Sections are washed first with water, then in water acidified with a little 

 nitric acid, and stained in concentrated solution of safranin. They are then 

 treated with alcohol and clove oil till no more colour comes away, and are 

 brought back again into water, washed in water acidified with acetic acid, 

 stained in methylen blue, and cleared as before. The process is said to de- 

 monstrate the existence of " chromoleptic zones " which surround the grey 

 matter. Myelin ("erythrophilous substance" of Adamkiewics) is red, nuclei 

 of nerves, of neuroglia, and of vessels violet. The erythrophilous substance 

 of pathological nerve-tubes does not take the stain, so that the method is 

 valuable for the study of degenerative changes. 



775. NIKIFOROW (Zeit. f. wiss. Mik., v, 3, 1888, p. 338) modifies the 

 foregoing method as follows : The tissue is to be hardened in a chrome 

 salt. It is not to be washed in water afterwards. Sections are brought 

 direct from alcohol into the safranin stain, either concentrated aqueous, or 

 Babes's solution, or a solution in 5 per cent, carbolic acid. Stain for twenty- 

 four hours. Bring the sections into alcohol until the colour is sufficiently 

 extracted for the grey substance to be distinguished from the white. Then 

 put them into a weak (O'l to 0'2 per cent.) solution of chloride of gold or 

 platinum or any metallic salt. They are to be left in this until the grey 

 substance just begins to get a violet tone (not longer). They are then well 

 washed in water, and put into alcohol until the rosy violet of the grey sub- 

 stance becomes distinctly marked off from the red of the white substance. 

 Clear with clove oil, wash out the clove oil thoroughly with xylol (this is 

 absolutely necessary for the permanence of the preparations), and mount in 

 balsam. Nikiforow says that this method gives much sharper and more 

 certain results than that of Adamkiewics. 



776. Purpurin, according to DUVAL, has a special action on nerve-tissue 

 (especially spinal cord) that has been hardened in bichromate of ammonia. 

 Nerve-cells and their processes, axis-cylinders and connective-tissue fibrils, 

 remain unstained, whilst the nuclei of connective tissue and of capillaries 

 stain red (see 201). 



Mounting . 



777. General Mounting Methods. Under this head it is to 

 be noted that it is often advisable to fix sections to the slide 

 before applying balsam, or other medium, and a cover. For 

 celloidin sections you may use one of the usual methods de- 

 scribed in Chap. XVII, or for large sections the gelatin 

 method of Fol, or Minot's shellac method. This is as follows : 



