Mauch 31, 1905. 1 



SCIENCE, 



485 



ready for use. A single cover-glass is re- 

 moved with clean forceps from the alcohol 

 and dried with clean linen without touch- 

 ing it with the fingers. It is then taken in 

 the forceps and passed several times 

 through the Bunsen flame. 



The fixing agent is a mordant and the 

 stain is carbol gentian violet or preferably 

 carbol fuchsine. 



Mordant.— 2 grams tannic acid; 5 grams 

 cold saturated solution ferrous sulphate 

 (aqueous); 15 c.c. distilled water; 1 c.c. 

 saturated alcoholic solution of fuchsine. 



To these ingredients I add a one per cent, 

 solution of sodiimi hydroxid, from .5 to 

 1 c.c. After filtering, the mordant should 

 be of a reddish-brown hue, and it must be 

 used within five hours after it is made. 



Carbol Fudisine. —Fnt about one gram 

 of granulated fuchsine in a bottle and pour 

 over it 25 c.c. of warm alcohol ; shake, let 

 stand for several hours, and dilute four or 

 five times with a five per cent, solution of 

 carbolic acid. 



A small loop full of the clouded water is 

 transferred to the cover-glass. A spread 

 consisting of several parallel streaks is 

 best. The glass, held by the forceps, prep- 

 aration side up, is passed down on to the 

 Bunsen flame and instantly removed. The 

 mordant is then poured on, just enough to 

 cover the surface without flowing over the 

 edges. After one half to one minute the 

 mordant is completely washed off under 

 the tap ; a small quantity of alcohol is then 

 poured on to the surface and instantly 

 washed oft". Then cover the surface with 

 carbol fuchsine or carbol gentian violet, 

 which is allowed to stand on the cover- 

 glass for about one half minute. We then 

 heat it so that steam is given off and, after 

 drying thoroughly, treat with xylol, im- 

 mediately draw off the xylol Avith filter 

 paper, drive off what remains with heat 

 and mount in xylol balsam. 



A Simple Method of MaJcing Photo- 



micrographs.— The camera is about twice 

 as long as the ordinary 4x5 camera, and 

 the photomicrographs are taken with the 

 camera in a horizontal position. It must 

 be steady and the microscope stand should 

 be substantial, with the fine cone adjust- 

 ment. Much depends upon the objective. 

 I have found none equal to the one-twelfth 

 oil immersion objective and No. 6 compen- 

 sating eye-piece made by the Spencer Lens 

 Co. The best plates are the isochromatic 

 or orthrochromatie swift plates which are 

 corrected for colors. I have found the 

 acetylene radiant preferable to gas, oil or 

 electric light. The only screen I ever use 

 is green glass. Printing from the nega- 

 tives on glossy Velox brings out the best 

 detail. The glossy Velox is then ferro- 

 plated, which makes a beautiful photo- 

 graph. 



(Complete paper will be published in the 

 New York Medical Journal; also in the 

 Canner and Dried Fruit Packer, 1905, 

 XX., No. 5, p. 23, with many illustrations.) 



Principles of Classification of Ba&teria: 

 F. D. Chester, Delaware Agricultural 

 College. 



As far as possible morphologic char- 

 acters should be the primary basis of classi- 

 fication. The generic system of Migula is 

 proposed, based upon character of flagella- 

 tion. 



With sporogenous bacteria, character of 

 spores, mode of germination, form of 

 sporangia, and orientation of the cellular 

 elements are useful toxonomically. With 

 the aspoi'ogeneous bacteria grouping must 

 be based largely upon physiological char- 

 acters. 



The proposed division of genera into 

 groups is based upon leading characters in 

 the order named : ( 1 ) Spore formation, 

 (2) relation to oxygen, (3) liquefaction of 

 gelatin, (4) fermentation of lactose, (5) 

 fermentation of dextrose, (6) fermentation 



