66 The Microscope. 



or quite fifteen years. I stated, in my various articles, that ob- 

 jections had been made to the cement by various microscopists, 

 and some of them men of prominence, but I also stated what I 

 again reiterate, that, in every instance where zinc cement dis- 

 appoints its user, it is because the article is improperly made, 

 or improperly used, or both. The learned doctor's habit of im- 

 punging tbe motives and cheapening the work of others is too 

 well known to make any answer to the balance of his article 

 necessary. To the motto of the ancient Pharisee, " I am more 

 righteous than thou," he seems to have also added, " I am more 

 skillful than thou," and hangs his banner on the outward wall 

 on every occasion, where it henceforth may float — for all that I 

 care. — Nat. Druggist. 



The Microscope continues as bright and newsy as ever, and, 

 for one dollar a year, is the cheapest periodical of the kind ex- 

 tant. Ann Arbor is its home. — Odontography Journal. 



Dr. L. Younghusband, of Detroit, has just received a letter 

 from Prof. Koch, of Berlin, with a microscopic slide of the 

 " Comma-bacillus," which is regarded by Dr. Koch and his fol- 

 lowers as the sole cause of cholera. 



Error in Photographing Blood-corpuscles. — A note on a 

 possible source of error in photographing blood-corpuscles, by 

 G. St. Clair, communicated to the Birmingham Philosophical 

 Society, is a fruitless attempt to explain as an optical illusion 

 Dr. Norris's asserted discovery by the aid of photography of a 

 third kind of corpuscle in mammalian blood. The author in- 

 vokes the principle of the formation of images by the passage 

 of light through small apertures, and conceives that Dr. Norris's 

 " colorless disks " are merely images at the end of the micro- 

 scope-tube or the aperture of the eye-piece, and he seems to 

 have taken some pains to obtain such images by placing under 

 the microscope a slide thickly strewn with small steel disks, 

 and receiving the light on a screen beyond the eye-piece. Had 

 he attempted to focus these ghosts and the real images of the 

 disks at the same time, or considered a little more closely the 

 elementary optical principles involved, we venture to sa} T they 

 would never have been written. — Royal Mic. Journal. 



