1882.] 



MICROSCOPICAL JOURNAL. 



163 



for purposes of verification. He has 

 a battery of lenses of narrow and wide 

 angles. The best lenses have as large 

 an angle as is compatible with re- 

 quisite focal depth. 



One point I wish to impress upon 

 American microscopists. It has been 

 claimed that low powers of high angle 

 are equal to higher powers ; that a^^ 

 with wide angle will do everything. 

 It will resolve tests, but its continued 

 use will injure the eyes. I never per- 

 ceived any injury to my eyes, not- 

 withstanding that J. Edwards Smith 

 said that my eyes were failing because 

 I could not see the difference be- 

 tween wide and narrow angles. Dr. 

 Dallinger believes if he had worked 

 with a }i instead of a ^ he would 

 have injured his eyes. I remember 

 the first ^ by R. Beck. It was a 

 good glass. To work up a ^ to 150" 

 destroys its value. I hear of Ameri- 

 cans making one-inch objectives up 

 to great angles, for which the society- 

 screw is too small. This makes a 

 very bad ^ and spoils it for a one- 

 inch. This conclusion is in entire 

 conformity with the mathematical re- 

 sults of Abbe. I have only stated the 

 conclusions we have generally come 

 to on the other side. High-power 

 eye-pieces are valuable for testing ob- 

 jectives. A good two-inch should 

 resolve the podura scale, with sufifi- 

 cient magnification from the eye- 

 piece. For ^10 or ^^12 a good set 

 of English objectives up to a yV'i'^ch 

 can be obtained, which is about the 

 cost of a single -^^ by an American 

 maker. 



In reply to a question of Dr. Tut- 

 tle, Dr. Carpenter stated that the ^ 

 used by Dr. Drysdale was a dry lens 

 of 140°. 



Prof. Burrill asked if Dr. Carpenter 

 intended to say that a high-angle lens 

 of high power was only good for the 

 resolution of lines. In reply, it was 

 st'ated that the flagella of Monas termo 

 would probably not have been found 

 without the wide-angle lens, but now 

 they are known to exist, they have 

 been seen better with a lower angle. 



In illustration of his position, Di. 

 Carpenter also referred to some obser- 

 vations with low powers of wide and 

 narrow angles used with the binocu- 

 lar, and instanced the structure of 

 the diatom Isthmia as revealed by a 

 Zeiss' % of 40° with the binoculac. 

 In speaking of the advantages of bin- 

 ocular microscopes, he mentioned as 

 a very beautiful object, a transparent 

 injection of brain, which, when once 

 seen with a low angle and binocular, 

 would never be looked at in any 

 other way. 



He also mentioned a trial of two 

 >^-inch objectives, by different 

 makers, of 90°, which he desired to 

 use for the study of Polycystina. The 

 perspective was so greatly exagger- 

 ated that they could not be used. He 

 procured stops which respectively re- 

 duced the angle to 60" and 40**. With 

 the full aperture of 90° the object 

 appeared like the small end of an egg, 

 with the stop of 60° it appeared 

 like the large end of an egg, with 

 the stop of 40° the perspective was 

 true. A ^-inch of 40° was then or- 

 dered of Powell & Lealand, who were 

 at first unwilling to make such a low- 

 angle glass, but finally did so, and at 

 a soiree of the Microscopical Society 

 'it was exhibited beside the 90° lens, 

 and the difference between them was 

 so striking as to attract universal at- 

 tention and commendation of the 

 low-angle lens. 



Dr. William Osier read a short ar- 

 ticle on 



MICROCYTES OF THE BLOOD 



and their probable origin. In brief 

 he said : Microcytes are exceedingly 

 minute, red blood-corpuscles about 

 1'^\t^ of an inch in diameter, which 

 are met with in the blood of em- 

 bryos and of the new-born, occasion- 

 ally in small numbers in the blood of 

 healthy individuals, in certain di- 

 seases, particularly the severer forms 

 of anaemia, and after hemorrhage. 

 No satisfactory explanation has been 

 given of their origin. The author has 

 seen their production in the spleen- 



