ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 839 



(the fluid penetrates tlie bone-cells and canaliculi). But a short heating 

 of tliiu plates is better. The author was able to distinguish Sharpey's 

 fibres in the soft and uncalcified condition from those partially calcified. 



Physiological Silvering of Elastic Tissue.* — Dr. A. Blaschko states that 

 in the cutis of silver-workers there are frequently found, in places exposed to 

 the light, blue-black spots, which are formed from the penetration of minute 

 fragments of metallic silver into the skin. It is obvious the silver is dissolved 

 in the skin, and separates out from the solution into very fine granules under 

 the influence of light. This reduction of silver takes place in the living 

 tissue, especially in the course of the elastic connective tissue, the fine 

 fibrillations of which are thus rendered manifest. 



Preparation of the Retina, j — Dr. P. Schiefferdecker finds the follow- 

 ing mixture preferable to Eanvier's alcohol as an isolation medium for 

 the retina : — Aqua destillata, 20 vol. ; glycerin, 10 vol. ; methyl alcohol, 

 1 vol. 



The eye, cut up, or only the retina is placed in this fluid for several 

 days. A small piece of the retina with some water is placed in a test-tube 

 and shaken up. It is then emptied into a watch-glass and some drops of 

 glycerin and of a cold saturated watery solution of picrocarminate of soda 

 added. It is then stirred up with a needle and placed in a sulphuric acid 

 drying apparatus. The red-stained retina elements are mounted in 

 glycerin. As this method is not always successful, several preparations 

 are necessary. For hardening, the author used Miiller's fluid, chromic 

 acid 1-600, and acetum pyrolignosum, one part to three parts distilled 

 water. The latter is especially recommended. Eyes of small animals 

 should be hardened in osmic acid or its vapour, and afterwards treated 

 with Miiller's fluid. These small eyes are best hardened before being 

 opened. 



Imbedding in celloidin. This must be allowed to soak in for some 

 days, and the cover removed little by little. When the ether and alcohol 

 have so far evaporated that the finger scarcely leaves an impression on the 

 celloidin mass, 50 per cent, spirit is poured in and the mass taken out the 

 next day, when it may be cut. The knife should always be kept wet with 

 spirit. Paraffin imbedding alters the retinal elements, and osmic acid is 

 to be avoided as it gives rise to deceptive appearances owing to precipitation. 



Preparing the Mammalian Testis. | — In investigating the mammalian 

 testis, Herr C Benda used the following reagents and methods. 



For hardening purposes, he imitated Biondi in the almost exclusive use 

 of Flemming's chromic-osmic-acetic mixture (I per cent, chromic acid 

 7 vols., 2 per cent, osmic acid 2 vols., glacial acetic 0'3-0-5 gr.). Con- 

 centrated picric acid and sublimate also yielded very fair results. The 

 imbedding, cutting, and fixing in albumen-glycerin were accomplished as 

 usual. Staining was effected by a modification of Heidenhain's and 

 "Weigert's haematoxylin method. The sections remain twenty-four hours 

 at about 40^ C. in concentrated solution of neutral acetic acid and oxide of 

 copper, are then carefully washed, darkly stained in aqueous solution of 

 haematoxylin, decolorized to a bright yellow in very dilute hydrochloric 

 acid solution (1:300-500). The acid is again neutralized, best in the 

 copper solution ; the sections become light bluish-green and are finally 

 dehydrated and mounted. The staining thus laboriously effected is very 

 well defined and gi-aduated, and is also persistent. The portions of testis 



* Arch. f. Mikr. Anat., xxvii. (ISSG) pp. G51-5 (1 pi.). 



t Ibid., xxviii. (1886) pp. 305-95 (3 pis.). J Ibid., xxx. (1887) pp. 49-110 (3 pis.). 



