ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



369 



bacteria substance, should be found for each case. In the Pathological 

 Department of the University of Vienna, A. Weichselbaum, and in the 

 Clinic for Skin Diseases, Finger, and more recently Landsteiner and 

 ]\Iucha, have proved that this new instrument is very convenient for 

 rendering visil>le the Spirochieta ixilUda. Further details are given in 

 the " Wiener khnische Wochenschrift," 1906, No. 45. 



Fig. 61. 



Pfund's Simple Photometer.* — A. H. Pfund has got very good 

 results from the following simplified form of the Lummer-Brodhun 

 type of photometer. A piece of plane glass about 2 mm. thick is 

 silvered, highly polished, and then cut in two ; the diamond scratch 

 being made on the "glass" and not on the "silver" side. If the 

 break is not perpendicular to the flat surface, that portion of the mirror 

 is selected which has an acute angle at the edge of the silvered surface. 

 Upon close examination, it will be found that the silver extends up to 

 the very edge, and hence, by using this arrangement as a photometer, 



* Johns Hopkins Univ. Circular, No. 186 (April 1906) pp. 20-22 (2 figs.). 



