20 



THE AMEEICAN MONTHLY. 



[January. 



identified bacteria, particularly abroad. 

 Mr. Emmerich has ordered a series of 

 preparations to meet such a demand here, 

 and will doubtless be prepared to fill or- 

 ders for them by the time this journal is 

 issued. Some of them are mentioned in 

 his advertisement, the most notable of 

 which is the comma bacillus of cholera. 



— Messrs. H. R. Spencer & Co. are pre- 

 paring a new price-list of their objectives, 

 which will doubtless be ready by the time 

 these lines are printed. With increased 

 facilities for manufacture and good busi- 

 ness connections, they propose to fill or- 

 ders more promptly than heretofore. They 

 now make a non-adjusting homogeneous 

 immersion objective of a new series, which 

 they maintain as 'hard to beat for finish, 

 price and power.' 



— The mounted preparations of patho- 

 genic bacteria, advertised by Dr. Abbott 

 this month, will doubtless prove very de- 

 sirable additions of the collections of mi- 

 croscopists and especially of physicians. 

 Dr. Abbott is assisting Dr. G. M. Stern- 

 berg in his laboratory, and therefore has 

 special facilities for obtaining pure cul- 

 tures of pathogenic bacteria, and patho- 

 logical material of an interesting nature. 



— Dr. Sternberg informs us that he has 

 just obtained a pure culture of the micro- 

 coccus of swine-plague, which was proved j 

 by Dr. D. E. Salmon to be the cause of i 

 the disease. Although Dr. Salmon's con- 

 clusions have been called in question by 

 Dr. Klein, the evidence upon which they 

 were founded is too strong to readily over- 

 throw, particularly since he has lately suc- 

 ceeded perfectly in producing the disease 

 with pure cultures. It is therefore inter- 

 esting to know that Dr. Sternberg has also 

 obtained the micrococcus. 



— Mr. T. Smith has called our attention 

 to an error in our last number, on page 

 225, where, in describing the method of 

 sterilizing the potato for cultures of bac- 

 teria, we stated that the cut slices should 

 be dropped into a solution of corrosive 

 sublimate. It appears that the object of 

 the corrosive sublimate solution is to kill 

 the spores on the outside of the potato — 

 attached to the skin — and the whole po- 

 tato is, therefore, dropped into the solu- 

 lution before the slices are cut. 



— What Mr. Tuffen West writes is 

 usually excellent, but when he tells us, as 

 in the Jourti. Post. Micr. Club, that ' black- 

 ground illumination is a poor way of get- 

 ting at the facts which a specimen may 

 disclose ; so also is polarizing,' we are not 



prepared to follow him so well as usual. 

 On the contrary, we should say that black- 

 ground illumination is sometimes abso- 

 lutely necessary to enable one to properly 

 study a specimen. We have in mind 

 just now an elegant preparation of a peris- 

 tome of a moss, and not only is it a far 

 more beautiful object when seen with a 

 dark field, but its structure is not fully re- 

 vealed in any other way. As regards 

 'polarizing,' by which is doubtless meant 

 the use of polarized light, what would a 

 mineralogist, for example, do without it ? 

 Surely Mr. West did not mean to make 

 such a sweeping assertion as his words 

 express. One might as well say — as Mr. 

 E. M. Nelson does — that the use of oblique 

 light in microscopy is not desirable. 



CORRESPONDENCE. 



Mosquitoes and their Scales. 



To THE Editor : — At the risk of pro- 

 voking jealousy between New Jersey and 

 Long Island, I will tell how I procured 

 the material from which my slide of mos- 

 quito scales, referred to in the November 

 number of the Journal, was obtained. 

 Driving on Long Island we encountered 

 a swarm of mosquitoes so thick that we 

 had to brush them away from before our 

 faces in order to see the horse. Bethink- 

 ing ourselves that we had with us some 

 large-mouthed ounce vials for collecting 

 purposes, we removed the cork from one 

 of them, and it was soon filled with live 

 and lively mosquitoes. Replacing the 

 cork, they died, but not until they had 

 well denuded themselves of their scales. 

 This was three seasons ago, and although 

 I have made many slides of mosquito 

 scales since that time, my supply shows 

 little signs of diminution. This may seem 

 like a mosquito story, but for its verifica- 

 tion I can still show those identical mos- 

 quitoes. M. A. Booth. 



LoNGMEADOW, MASS., Nov., 1884. 



Exchanges. 



[Exchanges are inserted in this column without 

 charge. They will be strictly limited to mounted ob- 

 jects, and material for mounting] 



Exchanges by list of all kinds of first-class material 

 for mounting solicited. A. M. BOOTH, 



Longmeadow, Mass. 



Unmounted material and labels for slides in ex- 

 change for good slides. 



EUGENE PINCKNEY, 



Dixon, III. 



Fossil Diatomaceous Earth, (a new find), very inter- 

 esting forms for other material. 



J. WALKER, 

 810 Twelfth Ave., South Minneapolis, Minn. 



