Herrick, MorpJiohgy of Brai?i of Bony Fislics. 339 



order to avoid loss in orientating in the microtome. It should 

 be remembered that the slightest overheating or contact with 

 water may vitiate the entire process at any stage in it. 



Previous to cutting the sections a dozen or so of oblong 

 glass trays, similar to devfeloping trays for photography, and 

 also a narrow glass vessel about two and three-quarters 

 inches high and two inches or less wide, are provided for the 

 reagents. The block is fastened in the microtome and orien- 

 tated, the superfluous paraffin cut away, and the block is 

 notched at one end to enable one to determine the position 

 of each section at a glance. A diagram of slide and intended 

 position of section and cover is made on paper and guide 

 pins are arranged to facilitate placing the slide. The slide 

 is brushed over with the albumen fixative, which consists of 

 one part of filtered egg albumen and two to three parts of 

 of glycerine. The fluid may be indefinitely preserved by 

 placing in the hood of the bottle a sponge moistened with 

 a few droys of carbolic acid. It is of first importance to 

 remove as much of the albumen as possible, as it is discolored 

 by the stain. One may wipe gently with a soft cloth, leav- 

 ing an almost imperceptible uniformly distributed film, 

 which will nevertheless adhere to the section. 



After the slide is furnished with its quota of sections, 

 which are carefully pressed upon the slide to avoid air- 

 bubbles, it is heated to the melting point of paraffin and 

 cooled before passing into a tray containing turpentine. 

 When the paraffin is completely removed the slides are 

 drained and washed with absolute alcohol from a dropper 

 and passed into 90 per cent, alcohol and thence into distilled 

 water. They are then covered with the stain, which is used 

 as dilute as possible, and allowed to stain until of a deep 

 blue color. After washing in water, the sections are passed 

 into alcohol, and ultimately are placed in the narrow vessel 

 above described filled with absolute alcohol. In order not to 

 vitiate the absolute alcohol too rapidly, the sections are flowed 

 with it before entering the vessel. They are then cleared 



