1898.] MICROSCOPICAL JOURNAL 107 



ical relation to the disease with which it is associated, by 

 Davaine, Pasteur, Koch, and others (1863-1875) ; the dis- 

 covery of the tubercle bacillus by Koch (1882) and the 

 discovery of the malarial parasite by Laveran (1879) — 

 these discoveries, so essential to the progress of scientific 

 medicine, would evidently have been impossible without 

 the aid of the compound microscope. While we owe much 

 to the methods of research devised by Pasteur, Koch, and 

 other pioneers in this line of investigation in the applica- 

 tion of these methods, the compound microscope is abso- 

 lutely indispensable, and, as medicine could not profess to 

 be scientific so long as we were ignorant as to the aetiology 

 of disease and of the histologic changes resulting from 

 disease processes, we must recognize the perfection of the 

 compound microscope as the most important event of the 

 century from our present point of view. The principle 

 involved in the construction of the compound microscope 

 was invented as long ago as in the sixteenth century, but 

 it is only within the present century, and principally 

 during the last half of the century, that those improve- 

 ments have been made which have made it available for 

 ^etiological and histological studies. There is, however, a 

 growing disposition to suspect that our microscopes, 

 notwithstanding the great degree of perfection attained in 

 their construction, are still inadequate to the task of 

 revealing to us the specific infectious agents of certain 

 diseases, because of their minute size. 



Gates' Double Microscope. This has been repeatedly 

 done before, and as often condemned. A second micros- 

 cope forms a most inefficient eye-piece. With regard to 

 deep eye-piecing, a 20-power eye-piece will easily render 

 visible, even to one possessed of ordinary vision, every- 

 thing that a %. inch objective of N. A. I'O (oil immersion if 

 you like) is capable of resolving. Edward M. Nelson. 



War. — On September 18, 1870, mail communication from 

 Paris was interrupted by the German investment of the 

 city. Balloons were at once resorted to and on Sept. 23, 

 25,000 letters were carried out by the " Neptune." Later 



