238 



THE AMEKICAK MOKTHLY 



[Decemberj 



and vegetable worlds ; and here, 

 moreover, with all reverence be it 

 said, we approach, if anywhere, the 

 confines of the organic and inor- 

 ganic, and are brought face to face 

 with that already half-lifted veil 

 behind which lies, waiting to 

 reward our patient search, the very 

 clue to the deep mystery of Life 

 itself." 



Diseases of Animals. 



The Department of Agricul- 

 ture has recently published a valu- 

 able volume which treats of " The 

 Contagious Diseases of Domesticat- 

 ed Animals." The investigations 

 have been continued since the pub- 

 lication of a former report on this 

 subject, principally by Dr. Detmers, 

 of Chicago, and Professor Law. 



Dr. Detmers finds that swine 

 plague is infectious and contagious, 

 and that it is easily communicable 

 by direct inoculation, and by the 

 presence of the infectious matter 

 in food or drinking water. He 

 thinks bacilli found in the blood 

 and other fluids, and in the excre- 

 tions of the animals, constitute the 

 infectious principle. Inoculation 

 with baccilli, cultivated in milk, 

 will produce the disease. The mala- 

 dy seems to be propagated by run- 

 ning water, in which the micro- 

 phytes may multiply, or by currents 

 of air which may carry the infec- 

 tion to the distance of a mile. Dr. 

 Detmers' report is accompanied by 

 a plate of numerous drawings from 

 the microscope. 



The report of Dr. D. E. Salmon, 

 who has been studying the Southern 

 cattle fever, is quite full and very 

 instructive. He considers that this 

 fever is probably caused by a living 

 poison, although he has not yet dis- 

 covered any fungus in the blood to 

 which the disease might be attri- 

 buted. A previous observer, how- 



ever, discovered a micrococcus ii 

 the blood of Northern cattle ■ 

 were affected with the disease. The 

 clear and logical manner in whicl 

 the subject is discussed is worthj 

 of the highest commendation. 



The remainder of the volume is 

 devoted to a consideration of pleurc 

 pneumonia, rinderpest, and seve 

 other diseases to which domestiH 

 cated animals are subject. 



CORRESPONDENCE. 



Oswego, N. Y., Nov., 1880, 



To THE Editor : — I had the othet 

 evening an opportunity to use that famous 

 yi that Mr. Willis has spoken so highly' 

 of, and it astonished me. I am not a very 

 expert manipulator, but I got the lines on 

 pellucida almost without trying, every 

 time. But I am not able to own so mag- 

 nificent and costly a glass. Last spring I 

 made up my mind that a 4-10 would be 

 one of the most convenient glasses I 

 could have, if one could be made of high 

 angle, having good resolution, large work- 

 ing distance, and so constructed that it 

 could be used upon opaque objects. I 

 wrote to Mr. Gundlach, asking him if he 

 could make such a glass of about 110°. He 

 seemed to think that I asked for contra- 

 dictory qualities ; the large working dis- 

 tance seemed the greatest difficulty. 

 Finally he made the glass. I can use it I 

 find, in examining water, without any 

 cover-glass, and by removing the cover of 

 the front lens, I can use it upon opaque 

 objects as readily as I could a one-inch of 

 60°, while I can resolve angulaiutn with 

 a 2_^-inch eye-piece, as an opaque object. 

 I have tried it with Gundlach's yi-mch. 

 periscopic eye-piece, and it gives good 

 light and fair definition. With a No. 3 

 eye-piece I get excellent definition and re- 

 solution, and can do anything that ordi- 

 narily needs to be done. With a ^-inch 

 eye-piece I get 500 diameters, and with 

 my aplanatic amplifier 1,000, and magni- 

 ficent resolution, while with a X-i"ch eye- 

 piece I get 1,000, without the amplifier, 

 and about 3,000 with it. So you see that 

 I have from 60 to 500 diameters within 

 easy range, and most perfect resolution 

 and definition, combined with large work- 

 ing distance, a thing which I have never 



