iS93. SOME USEFUL METHODS IN MICROSCOPY. i2i 



otherwise altered. They were then washed in running water under 

 the tap for at least 24 hours. It is frequently necessary to wash 

 objects in this way, and when they are small they are liable to be 

 lost. I may recommend, therefore, the followng simple and absolutely 

 safe piece of apparatus. A piece of thick glass tubing, about nine 

 inches long, is closed at one end by having a piece of gauze tied over it. 

 It is then supported ^\'ith the closed end downwards in a vessel about 

 six inches in depth, which stands in the sink.^ The object to be 

 washed is placed in the tube on the gauze, and water is allowed to 

 trickle from the tap into the upper open end of the tube. The water 

 passes over the object and through the gauze into the outer vessel. 

 When the latter is full it overflows down the sink. In this way even 

 very minute objects can safely be left all night exposed to the current, 

 provided they cannot pass through the gauze. At the same time 

 they are in the direct current. 



The testes after being thus washed were hardened in alcohol and 

 cut into sections, and stained on the sHde with various anilines,^ and 

 in this way most successful preparations of nuclear figures were 

 obtained, giving a beautiful differential stain in combinations of 

 different anilines. I have also obtained very good sections of Lmn- 

 bviciis in this manner, but here, unless the sections are very thin, they 

 require to be bleached before staining, owing to granules in the cells 

 being blackened by the osmic. Bleaching was done by placing the 

 shde of sections in a bottle of 80 per cent, alcohol, having 

 previously covered the bottom of the vessel with a layer of crystals 

 of chlorate of potash.* A few drops of concentrated hydrochloric 

 acid were then cautiously added, and the bottle subjected to shght 

 warmth (by placing it on the paraffin bath). In about an hour's 

 time the chlorine evolved has bleached the sections. 



I have above briefly mentioned a method of fixing the cephalopod 

 blastoderms on to thin slices of liver in order to section them. This 

 method is also so useful for orientating minute objects in paraffin for 



6 It is not, of course, in any way necessary that the glass tube and the vessel 

 should be nine inches and six inches in height respectively, but only that the tube 

 should be considerably longer than the vessel is deep, in order that the water which 

 runs through is obliged to pass through the gauze, and cannot overflow from the 

 top of the tube. 



7 For all the anilines used, namely, Safranin, Gentian Violet, Eosin, Fuchsin, 

 Fuchsin S., Dahlia and Orange G., the following recipe (recommended by 

 Hermann, loc. cit.) was used for making up the solutions: — 



Staining substance (dry) . . . . . . . . . . i gramme 



Absolute alcohol . . . . . . . . . . . . 10 cc. 



Aniline water . . . . . . 90 cc. 



Anilines made up in this way stain very intensely and sharply, washing out being 

 done in absolute alcohol. Safranin may, however, be washed in acid alcohol. 

 These solutions do not, however, keep very long, especially Gentian Violet, Eosin, 

 and Dahlia, and require to be used fresh. 



*This method was, I believe, first described by Kiihne, as a means of depigment- 

 ing retina ; it can be used both for objects in toto, or, as here described, for sections 

 on the slide. 



