202 PRACTICAL MICROSCOPY. 



franin is preferred by Strassburger. A saturated solution of the dye 

 in absolute alcohol is diluted with an equal volume of water and al- 

 lowed to act on the tissue for twenty-four hours. Wash thoroughly 

 with absolute alcohol, clear in oil of cloves, and mount in dammar. 

 The highest powers are necessary for successful demonstration. 



FIXING AND STAINING THE CORPUSCULAR ELE- 

 MENTS OF BLOOD. 



The following method, which has been elaborated by Prof. Gaule, 

 of Zurich, will prove more satisfactory than processes which involve 

 the drying of the blood. The essential steps are: 



1. Transferrence to the slide. This must be accomplished very 

 quickly to provide against changes in the corpuscular elements which 

 occur soon after removal from the vessels. If to be taken from the 

 living animal and the frog is best for beginners the surface must be 

 scrupulously clean, a small vessel punctured with the needle, and a. 

 minute drop of blood carried to the surface of a slide by means of a 

 glass rod. The blood is spread in a thin layer, after which, and be- 

 fore drying, the elements are to be fixed. 



2. Fixing. A portion, say fi. ij., of a saturated aqueous solution 

 of bichloride of mercury having been prepared in a saucer, the blood 

 slide is submerged in the liquid. Five minutes suffice for this work. 



3. Washing is accomplished by immersing the slide for a moment 

 in a saucer of distilled water, after which the action is completed by 

 placing in absolute alcohol for five minutes. Drain on bibulous 

 paper for a moment. 



4. Staining. Moisten the blood with a little distilled water, drain, 

 and afterward drop a few minims of haema. solution on the horizon- 

 tally placed slide. Ordinary haema. will answer perfectly if, to about 

 a drachm of the solution, two drops of alcohol are added. The stain- 

 ing is complete in five, minutes. Wash in distilled water, and again 

 stain as before with a one-per-cent aqueous solution of nigrosin. 

 Again wash with distilled water, and again stain as before with eosin 

 one part, alcohol 50 parts, distilled water 150 parts, for one minute. 



5. Mounting. A permanent specimen is completed by washing 

 the film of blood with strong alcohol. A drop of oil of cloves gives 

 transcluceucy in a moment, after which it is drained off, a drop of 

 dammar added, and the cover applied. 



The nuclei of the red corpuscle of the frog take the blue haema. f 

 while a variety of white corpuscle with a large round or spindle-shaped 

 nucleus the hcematoblast of Hayem has its protoplasm stained 



