ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1051 



he seems to have had came from a combination of methyl-violet 

 or dahlia, with eosin or acid fuchsin. The sections hardened in 

 absolute alcohol are stained with an aqueous or weak spirituous solution 

 of methyl-violet for five minutes, they are then transferred to a very 

 dilute solution of eosin in spirit, wherein they remain for one or two 

 minutes. After this they are again treated with spirit and mounted in 

 the usual way. 



Safranin as a Stain for the Central Nervous System.* — It has already 

 been pointed out, says Dr. M. Nikiforow, that safranin stains certain 

 parts of the central nervous system in a characteristic way when the 

 tissue has been hardened in chromic acid salts. Thus the medullary 

 sheath of the fibre (erythrophilous substance) stains rose, while the 

 nuclei of the nerves, glia cells, and blood-vessels assume a violet hue. 

 This property of safranin is all the more important, because in disease, 

 and even in the earlier stages thereof, the characteristic coloration is 

 lost. The method of the author for manipulating the tissue in order to 

 obtain a satisfactory result, as far as difi"erentiation is concerned, is as 

 follows : — The brain or cord is hardened in chromic acid salts (Miiller's 

 fluid or bichromate of ammonium). The chromic acid salts are not to 

 be washed off with water, and the sections are to be transferred directly 

 from spirit to the concentrated aqueous solution of safranin. The 

 anilin water solution or a 5 per cent, carbolic acid solution of this dye 

 may be used. It is advised to over-stain the sections or to leave them 

 in the staining solution for 24 hours. After this the sections are re- 

 moved to spirit, where the excess of stain is washed off. As soon as the 

 grey substance begins to appear, and can be distinguished from the 

 white matter, the section is lifted out and placed in a solution of a 

 metallic salt, chloride of gold, or chloride of platinum, the strength of 

 which is 1 : 500 and 1 : 1000. When a trace of violet begins to show in 

 the grey substance the section is at once placed in water and thoroughly 

 washed. After this it is placed in alcohol until the rose-violet of the 

 grey substance is clearly distinguishable from the red of the rest of the 

 tissue. It is next cleared up in oil of cloves, and the latter replaced by 

 'xylol, and finally the specimens mounted in balsam. 



Combining Weigert's Hsematoxylin-copper Stain for Nerve-fibre 

 with the use of the freezing Microtome.j — Prof. D. J. Hamilton states 

 that sections of brain of any size can be cut with the freezing microtome 

 and stained to perfection with the copper and htematoxylin if the 

 following method be adopted. 



The brain should be hardened in Miiller's fluid, the longer the better 

 those which have lain years in the fluid being best to work on! 

 Human brain requires three to four months, and that of a small animal 

 three to four weeks. When thoroughly hardened it is cut into perpen- 

 dicular transverse slices, about half an inch thick, and these are allowed 

 to lie in Miiller's fluid two or three weeks longer, and may be kept in 

 this indefinitely. They are then cut into pieces required to fit the micro- 

 tome, and these are placed in ordinary methylated or absolute alcohol 

 for three days, the _ spirit being changed each day. From this they are 

 transferred to a mixture of equal parts pure alcohol and ether, in which 



* Zeitschr. f. Wiss. Mikr., v. (1888) pp. 338-40. 



t Journ. of Anat. and Physiol., xxi. (1887) pp. 444-9. 



