INVERTEBBATA, CRYPTOGAMIA, MICROSCOPY, ETC. 311 



that the small rod-shaped bodies that are always found in the cells of 

 the leprous tubercles are either masses of zoogloea or collections of 

 bacilli enclosed in cells. He has not yet succeeded in a more exact 

 determination of the organism. 



Influence of the Electric Current on the Development of Bacteria.* 



— According to a careful series of experiments carried on by Professor 

 Cohn and Dr. B. Mendelsohn, the following are some of the most 

 important effects produced on the propagation of bacteria by the 

 galvanic current : — 



As respects the increase in mineral nutrient fluids : A single 

 element has no effect, or only a retarding one, on the increase of 

 bacteria. A battery of two powerful elements completely sterilizes 

 the solution at the jiositive pole in from twelve to twenty-four hours ; 

 at the negative pole it is not completely sterilized ; but at neither pole 

 are the bacteria killed ; when removed to a fresh solution they continue 

 to propagate. They are, however, completely killed within twenty- 

 four hours by a battery of five powerful elements 



A second series of experiments referred to the effects of a constant 

 galvanic current on the development of Micrococcus jprodigiosus on the 

 surface of boiled potatoes. Both at the positive and negative elec- 

 trodes the increase of the micrococcus was prevented in the immediate 

 vicinity on both sides, but much more completely at the positive 

 electrode. When the current was weaker, there appeared on both 

 sides of the positive electrode a broader or narrower, sharply-defined, 

 colourless strip, while on both sides of the negative electrode the 

 development of the micrococcus was prevented in only a very narrow 

 zone. The more powerful the current, the broader was the zone at 

 both electrodes whore the increase of the micrococcus w'as prevented. 

 When the current was very powerful, it was altogether sujjpressed ; 

 the germs were killed and both halves of the potato sterilized with 

 the exception of the neutral boundary-line. 



Presence of Bacteria in the Air.t — A large series of experiments 

 on the suspension of bacteria in the air, carried on at Breslau by Dr. 

 Miflet, of Kiew, under the superintendence of Professor Cohn, have 

 led to the following results : — 



1. A number of bacterial germs capable of germination are sus- 

 pended in the air. 



2. By means of an apparatus constructed for the purpose, and 

 which is fully described, the germs may bo collected, made to germi- 

 nate, and systematically determined. 



3. The larger number of gta-ms thus detected in the air wero 

 those of micrococci and bacilli. Most of these were already known as 

 growing in other media ; some were of very peculiar and liithcrto 

 unknown forms. 



4. Many bacteria, on tlic other hand, ordinarily found in ferment- 

 ing substances, were not detected in the air ; tliis is true especially of 

 Bacterium Tvrnw, the ordinary ferment of putrefaction, Spirillum, 

 SpirochoBtc, and some others. 



♦ 'Beilr. Hiol. I'llauz.' (Culm)., iii. (1S7'.») i>. 111. f Ibi.]. p. U;», 



