10 THE AMERICAN MONTHLY [January, 



nuclei, stained blue, appear. Their outlines are indistinct and the color 

 gradually changes to green. The cilia remain colorless. After four to 

 five hours all the nuclei become stained emerald-green and only a very 

 few cells remain colored violet. 



The author has also found that methyl green prevents the coagulation 

 of blood. A \% solution in a f-% aqueous solution of sodium chloride 

 retards the coagulation, when used in the proportion of 2 c.c. to 40 c.c. 

 of blood. In the proportion of 3 to 4 c.c. to 40 c.c. of blooc it en- 

 tirely prevents the coagulation. 



Method of Making Sections of Teeth and Bone with the 

 Preservation of the Delicate Parts. — Weil, Zeitsch. f. Wiss. 

 Mikros. v, 1S8S, p. 300. 



The fresh tooth is broken in half and placed in a concentrated solu- 

 tion of mercuric chloride for one hour ; then in 30% alcohol. After 

 24 hours this is replaced with 50% alcohol, and at the end of another 24 

 hours by 70%. After 12 hours the tooth is placed in a mixture of 

 100 c.c. of strong alcohol and 2 c.c. of the tincture of iodine, for the 

 removal of the black precipitate of mercury. This requires about 12 

 hours, The iodine is then removed by washing in strong alcohol, 

 which is renewed as long as it becomes colored. 



The specimen is now to be stained. For this purpose, the author 

 recommends either an aqueous or alcoholic solution of borax carmine. 

 The specimen is removed from the alcohol, washed in water, frequently 

 changed, for half an hour, and then placed in the staining fluid. The 

 aqueous fluid requires 1 to 2 days ; the alcoholic fluid 2 to 3 days for 

 staining. When the staining is complete, place the specimen in acidu- 

 lated alcohol [70% alcohol 100 c.c, Hcl. 1 c.c] for 12 hours if the aque- 

 ous solution has been used, and for 24 to 36 hours if the alcoholic stain- 

 ing fluid has been used. Then in 97% alcohol for 15 minutes, double 

 this time in absolute alcohol, and finally in an etherial oil for 24 hours 

 or more. 



On removing the specimen from the oil, wash quickly in xylol and 

 place in chloroform for 24 hours ; then in a solution of chloroform 

 and hard Canada balsam for 24 hours ; then add to this solution as much 

 of hard balsam as it will take up, and pour the specimen with as much 

 of the balsam as will cover it into a porcelain dish. Place the dish on 

 a water-bath and heat gradually to 90 C. ; keep at this temperature 

 until a sample of the balsam becomes hard like glass upon cooling. 



Thin slices are now cut oft" with a fine saw, wet with cold water. 

 These are ground and polished in the usual manner, and finally mounted 

 in hard balsam dissolved in chloroform. 



An Easy Method of Reproducing. Photographically, Histo- 

 logical Sections. — Tambusti, Zeitsch. f. Wiss. Mikros. v, 18S8, p. 



335- 



The author covers a piece of board with several layers of black cloth 



and stretches on this a small strip of albumen paper, sensitized with 



silver nitrate. The slide containing the specimen to be reproduced is 



placed upon this paper, cover side down, firmly clamped to the board, 



and the whole exposed to direct sunlight until the paper becomes 



sufficiently blackened. The print is then developed in the usual way* 



In place of the sensitized albumen paper the ferrocyanide of iron paper 



used for making blue prints may be used. 



