8 THE AMERICAN MONTHLY [January, 



The advantages claimed for the apparatus are these : Not more than 24 

 hours is necessary for dehydrating and hardening nearly all kinds of plant 

 tissue. The apparatus does away with the transferring of the tissue 

 from bottles containing alcohol of different strength, and as no sudden 

 transition from solutions of different strength occurs the tissue is less 

 liable to shrink. The simplicity of the apparatus places it in the reach 

 of all. Many different materials maybe used for a diaphragm, and 

 almost any desired speed of dehydrating obtained. The apparatus can 

 also be made of any size to adapt it for private or general Lab. work. 



It would seem that such an apparatus would work equally well for 

 animal tissue, but as yet I have not been able to make an extended trial 

 of it ; however, in the case of some insects hardened in it, it was found 

 to be admirably adapted to the purpose. 



Microscopy for Amateurs. 



By T. charters WHITE, 



yUEKKTT CLUB. 



{^Continued from f age ^75, vol. a/.] 



Staining Tissues. — Staining has added a fresh power to the mi- 

 croscope, for without its aid the highest magnification would fail to 

 show many interesting details. Staining may be general or selective ; 

 by the first, nothing is learned, but it is useful sometimes in showing up 

 the structures which are too transparent to be seen otherwise, and is 

 of great service, when the object is to be photographed, in presenting 

 a contrast against the general field of view. By selective staining, 

 which selects the growing parts of a tissue, the nuclei ai^e brought into 

 view, and the formed material is differentiated from that which is in 

 process of formation. 



Some histologists prefer to stain the hardened tissue before cutting, 

 which is followed by very good results ; but staining the section is just 

 as easily done without requiring so long an immersion as staining it in 

 the mass. The stains can be procured all ready prepared, but there 

 are one or two which are made without any difficulty, and which the 

 student can readily make for his own use ; they are carmine, logwood, 

 and picric acid. Dr. Beale's directions for making the carmine stain, 

 are: "Carmine, 10 grains ; strong liquor ammonia, ^ drachm ; Price's 

 glycerine, 3 ounces ; distilled water, 2 ounces ; alcohol, \ ounce. The 

 carmine in small fragments is to be placed in a test tube, and the 

 ammonia added to it. By agitation, and with the aid of the heat of a 

 spirit lamp, the carmine is soon dissolved. The ammoniacal solution 

 is to be boiled for a few seconds, and then allowed to cool ; after the 

 lapse of an hour, much of the excess of ammonia will have escaped. 

 The glycerine and water may then be added, and the whole passed 

 through a filter or allowed to stand for some time, and the perfectly 

 clear supernatant fluid poured oft' and kept for use. This solution will 

 keep for months ; but sometimes a little carmine will be deposited 

 owing to the escape of ammonia, in which case one or two drops of 

 liquor ammonia to the four ounces of carmine solution maybe added." 



Logwood stain may be made easily from any of the numerous for- 

 mula. " Take logwood extract 6 parts, alum 6 parts, sulphate of cop- 



