ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 219 



length. From this series one group that appears identical with the 

 organism fixed upon is noted, and the number of this group is multiplied 

 by the length of the organism. The result is the breadth. The breadth 

 of another organism in the same film may be calculated in a similar 

 manner, and the second result will generally be identical with the first. 

 For example, the rodlet measures l"5ft, and on comparison with the 

 diagrammatic table it appears identical with the group whose type 



On multiplying 1*5 /x by 0'4, the breadth 

 The result may be checked by measuring with the 



number 



breadth \ . 



_ — ) is 



leiigrth / 



0-6 /jl is obtained. 



Fig. 36. 



micrometer eye-piece. The diameters of cocci, streptothrix, &c, might 

 be confirmed after micrometer measurement by comparison with lines 

 ruled at intervals of 1 • 2 mm. (the length of the smaller diagrammatic 

 organisms) upon a cover-glass which is superposed over the shorter 

 diameter of the diagrammatic types. Such rulings can be made upon a 

 cover-glass by dipping the latter into a dilute solution of gelatin 

 (0*5 p.c), and ruling the lines with Indian ink upon the thin dry 

 gelatin film. 



Examination of Arsenical Sublimates. * — M. H. Stiles has found 

 that the examination of the arsenical sublimate under the Microscope 

 is much facilitated by the adoption of the following method. A strip 

 of copper foil, after having been boiled with 200 ccm. of the suspected 

 fluid (beer) and 30 ccm. of pure hydrochloric acid for 45 minutes, 

 is washed successively with water, alcohol, and ether, and dried. 

 The strip is then placed in a dry test-tube 3^ in. by £ in., containing 



* Pharmaceutical Journ., lxvi. (1901) p. 4. 



