282 THE AMERICAN MONTHLY [Sept. 



been carefully measured by Dr. Dallinger, who had found that 

 they had a width of only the 1-200,000 of an inch. It was quite 

 a triumph to reproduce these microscopic objects photograph- 

 icalh'. 



The lecturer next dealt with examples which, by speedy and 

 convincing comparison, would serve to set at rest questions 

 in which opinion was divided. He showed two preparations of 

 nerve cells, the one being properly " fixed," and the other being 

 faulty in that respect, giving rise to appearances which might 

 lead a student into error. Examples were also shown of cer- 

 tain newly discovered bodies which were found in cancer, the 

 real and the spurious being readily distinguished by the com- 

 parative method. 



The next slides shown were of very great beauty. They were 

 " culture plates," which had been exposed for five minutes, the 

 one in the comparatively pure air of Wadsworth Common, and 

 the other in a wide street. The first-named showed only a few 

 traces of bacteria, but the second was crowded with thick col- 

 onies of them. The advantage of at once obtaining photographic 

 records of preparations subject to such quick growth and other 

 changes as these culture plates are, was fully pointed out by the 

 lecturer. In a demonstration of some particular points where 

 only exceptional microscopic preparations are available, the 

 lecturer showed as examples (1) the position of the bacillus of 

 lepros}' in regard to cells and nuclei, and (2) the position of 

 the organisms in certain vessels in a rare form of skin disease. 

 In this last demonstration three slides were exhibited of the 

 same section, each under a different amount of magnification. 

 In the first, taken with a low-power objective, the organisms 

 were hardly visible; in the second they were plainly seen ; and 

 in the third, where the magnification was 1000 diameters, they 

 came forth in all their hideous detail. Some specimens of lan- 

 tern slides, colored by the Lumiere method, elicited the fact 

 that, although the original preparation was well imitated so far 

 as the staining was concerned, the advantage gained was more 

 than counterbalanced by loss of crispness, and the lecturer ex- 

 pressed a doubt whether, under such conditions, there was any 

 gain at all. 



In order to convey an idea to his audience of the actual mag- 

 pitude of so^ie of these microscopic objects, the lecturer threw 



