ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 427 



in the case of certain objects which had a capacity for it, also that 

 it depended on the size of the polarizing prism and other causes. 

 No doubt these did affect it to some extent, but he was of opinion 

 that the effect was largely a question of what the object was mounted 

 in. He did not find that Canada balsam was the best medium ; in 

 fact, the best effects were obtained by mounting in glycerine, when 

 there was very little difficulty in making out the details, and the 

 object looked brighter upon a blacker ground as contrasted with its 

 appearance when mounted in balsam. He thought the idea would be 

 found worth attention, especially where it was desirable to examine 

 objects under various conditions of direct and oblique light. 



Mr. T. C. White, in the discussion which followed, said that he 

 had always found a good deal of difficulty in using polarized light on 

 objects mounted in glycerine ; while Dr. Matthews, on the point of 

 the superiority of glycerine over balsam for the kind of examination 

 in question, described his experience as rather the reverse of 

 Mr. Michael's. Whether this arose from any difference in the objects 

 he could not say, but he thought the effect was probably due to some 

 difference in their density ; the only way of settling the point would 

 be to mount the same objects in both ways. He also thought that 

 with extremely oblique light, they got fringes of colour — probably 

 owing to diffraction. Mr. Michael had been very successful in getting 

 dark-ground illumination, but there appeared to be some curious 

 effect produced by a spot lens, less colour being produced in that way 

 than without, although it might be supposed that the contrary would 

 be the case. As to the differentiation of tissues, precisely the same 

 effects were obtained as by staining, but with the advantage that a 

 harmonious appearance was always produced, whereas with staining 

 the selective power caused differences of colour which were not 

 always harmonious. 



Wickersheimer's Preservative Liquid.* — To the wet and dry 

 methods of preserving with this liquid G. Brosike adds a third, the 

 "damp" method. The subject is injected with the liquid, and the 

 separate parts are moistened with it during dissection, and then en- 

 closed in an air-tight vessel. The method is suited to nerves, tendons, 

 fasciae, vessels, and ligaments; muscles become bleached under its action. 

 It appears to have no real advantages over a proper treatment with spirit, 

 and the fact of the liquid containing poison must be borne in mind. 



Brosike takes this occasion to coi-rect an important printer's error 

 in the official patent.j Instead of 10 grammes of arsenious acid it 

 should be 20 grammes. 



Preparing Haemoglobin Crystals. J— By using pyrogallic acid, 

 C. Wedl has prepared for studying with the Microscope, spectro- 

 scope, and polariscope, haemoglobin crystals from the blood of man, 

 other mammals, and frogs. The best plan is to remove the colouring 



* Centralbl. f. med. Wiss., ii. (1880) pp. 17-19. Of. Jahresber. Anat. Physiol., 

 ix. (1880) p. 82. 



t See this Journal, iii. (1880) pp. 325-6. 



X Virchow's Archiv, Ixxx. (1880) p. 172. Of. Zool. Jahresber. Neapel for 

 1880, i. p. 57. 



2 F 2 



