ZOOLOGY AND BOTANY. MICROSCOPY, KTC. 237 



durable as balsam mounts, and that a much greater variety of staining is 

 possible than in the case of glycerin mounts. After fixing and washing 

 in water, the general outline of the method is as follows : — (1) 10 p.c. 

 glycerin until concentrated. (2) Wash the glycerin out thoroughly 

 in 95 p.c. alcohol. (3) Stain ; use stains dissolved in al)out 90 p.c. 

 alcohol. (4) Wash in 95 p.c. alcohol, and complete the dehydration in 

 100 p.c. alcohol. (5) 10 p.c. Venetian turpentine in an exsiccator 

 until the turpentine becomes thick enough for mounting. (6) Mount 

 in the Venetian turpentine. 



While this is the general outline, it is not sufficiently definite for a 

 working introduction. The following concrete examples, describing the 

 use of Venetian turpentine with an aijueous stain, with an alcoholic 

 stain, and with a combination of aqueous and alcoholic stains, will l)e 

 more practical than general directions. The steps from fixing to mount- 

 ing, as used with an aqueous stain, will be described first, since this will 

 introduce the method in its least complicated form. 



Haidenhnin' s Tron-hsematoTylin. — Using Spirogyra as a type, proceed 

 as follows : — (1) Fix 24 hours in chromo-acetic acid : I p.c. chromic- 

 acid, 70 c.cm. ; glacial acetic acid, ;> c.cm. : water, 90 c.cm. The 

 volume of the fixing agent should be at least 100 times that (\i the 

 material to be fixed. (2) Wash in water, 24 hours. (;>) 2 p.c. aqueous 

 solution of ammonia sulphate of iron, 2 hours. (4) Wash in running 

 water, 20 minutes. If running water is not availaltle, wash in a large 

 quantity of water and change frequently. (5) Stain over night, or 

 24 hours, in h p.c. aqueous solution haimatoxylin. (6) Wash in water, 

 20 minutes. (7) 2 p.c. acjueous solution of ammonia sulphate of iron, 

 until the stain is satisfactory. This can be determined only by examin- 

 ing fre(]uently under the Microscope. (S) Wash in water, 2 hours. If 

 this washing is not thorough, the continued action of the iron-alum will 

 cause the preparations to fade. (9) Transfer to 10 p.c. glycerin, and 

 allow the glycerin to concentrate until it has the consistency of pure 

 glycerin. It is not necessary to use an exsiccator. Merely put the 

 glycerin into shallow dishes, and leave it exposed to the air, but pro- 

 tected from dust. If the material is in Petri dishes, or other dishes 

 with a large surface, three or four days will be sufficient. This process 

 should not be hastened by warming. (10) Wash out the glycerin with 

 95 p.c. alcohol. It will be necessary to change the alcohol several times. 

 From 10 to 20 minutes will be suflficient if the alcohol is changed 

 frequently. (11) Complete the dehydration in 100 p.c. alcohol: 

 10 minutes should be sufficient. (12) Mo.^t failures are. now ready to 

 ■occur. 



From the absolute alcohol the material is transferred to a 10 p.c. 

 solution of Venetian turpentine in absolute alcohol. The turpentine 

 thickens as the alcohol evaporates, and when it reaches the consistency 

 of pure glycerin the material is ready for mounting. The 10 j).r. 

 Venetian turpentine is very sensitive to moisture, and most failures are due 

 to this characteristic ; consequently the concentration cannot be itllowed 

 to take place with the turpentine exposed to the air of the room. Use 

 an exsiccator. This will not only absorb the moisture from the air, 

 ■but will soon remove the alcohol from the turpentine mixture. Make 



