358 THE AMERICAN MONTHLY [Oct. 



with xylol balsam are applied. The result is excellent. 

 If one wishes to search for crescents, a good plan is to 

 make the film fairly thick, to fix with alcohol, and then to 

 wash out the haemoglobin with very weak acetic acid, two 

 or three drops to the ounce of water. The now colorless 

 film is again washed, stained with methylene blue, and 

 mounted in xylol balsam in the usual way. The field not 

 being obscured by blood-corpuscles, the large amount of 

 blood which this method of preparation enables us to pass 

 rapidly in review greatly favors the quick finding of any 

 crescents that may be present. The same-method of pre- 

 paring blood films is equally applicable for the demonstra- 

 tion of other blood parasites. — British Medical Journal. 



Preservation of Microscopic Specimens. — Tores de- 

 scribes a method, which he has tested for a year and a 

 half, of preserving organs and tissues so that they retain 

 the color they had when fresh. He finds that five to ten 

 parts of a forty-per-cent. solution of formalin alone cause 

 the organs after a time to assume a tint which differs very 

 considerably from the natural color, but that if, instead of 

 water for diluting the commercial formalin solution, a so- 

 lution of one part common salt, two parts of magnesium 

 sulphate, two parts sodium sulphate in one hundred parts 

 of water be used, the color of the blood is well preserved. 

 Further, material preserved in such a solution is better 

 adapted for subsequent microscopic examination, since 

 the protoplasm of the cell is less altered and the nucleus 

 stains better and more deeply. The. method he adopts is 

 as follows: The material must be not too long washed in 

 water, and should be left in the formalin solution for a 

 period depending upon their size and thickness. A kid- 

 ney or spleen requires two days immersion, and the solu- 

 tion should be changed once or twice, or until the forma- 

 lin solution no longer gives a dirty brownish-red color. 

 Care must be taken to bring all portions of the object into 

 contact with the solution, and the object must be given 

 the shade which it is to retain permanently, since the 

 formalin solution causes it to assume a consistency such 



