874 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of the nervous elements). When the fibres are the object in view, 

 hardening should be effected in bichromate of potash, but if good 

 images of nerve-cells be desired, alcohol should bo employed. The 

 latest modification of Weigert's hematoxylin should be used for 

 staining nerve-fibres, but anilin colours are necessary for the cells. 

 Magenta, dahlia, and vesuvin are especially suitable. 



The procedure is as follows : —Harden and cut in 95 per cent. 

 alcohol. Stain in a watery solution warmed to evaporation. Wash 

 in 95 per cent, alcohol. Clear up in oil of cloves. Pass through 

 benziu to Canada balsam. The author lays especial stress on con- 

 trolling the results by simultaneous examination of the cortex of a 

 normal brain. 



Preparing the Iris of Man and Vertebrates.* — Dr. J. Kogane'i 

 removes the pigment epithelium, when not required for examination, 

 by the aid of a fine camel's hair brush. The removal is facilitated by 

 allowing the iris to remain in Miiller's fluid for a longer time than 

 usual. The pigment masses within the iris substance are decolorized 

 by immersion in chlorine water for a few hours. When the pigment 

 assumes a light brown tone, the specimen should be removed, as too 

 long action of the chlorine water destroys the tissues. Peroxide of 

 hydrogen gives no better results. The endothelium of the bird's 

 iris can be demonstrated without the aid of the silver treatment, 

 which is more especially suitable for the iris of white mice, rats, and 

 rabbits. A fresh bulb is fastened down on its posterior pole", the 

 cornea is snipped off, and a 0*25 per cent, silver solution is carefully 

 dropped on the exposed iris by means of a pipette, until the silvering 

 is sufficient. The iris is then cut out and. inspected in toto. Any 

 damage to the iris is thus avoided. 



In order to show the posterior limiting membrane of the human 

 iris devoid of nuclei and pigment, the author gives the following 

 method : — The posterior iris pigment is brushed with a fine fairly 

 stiff brush, until the pigment is to some extent removed from the 

 radiating folds. The posterior surface is then carefully scraped with 

 a scalpel, thus retaining the part of the boundary membrane which 

 is made up of fine radiating fibres. These fibres swell and become 

 pale in acetic acid, become brittle in 20 per cent, nitric acid, but 

 remain firm and separate from one another easily in 30 per cent, 

 caustic potash. The fibres are unaffected in trypsin solution. The 

 limiting membrane takes up colouring matter with difficulty. Eosin 

 answers best. Carmine and hematoxylin not well. Picric acid and 

 palladium chloride stain it and the connective tissue yellow. 



Preparing the Retina. f — Dr. W. Krause describes a variety of 

 methods for preserving, hardening, staining, and imbedding the 

 retina. 



A 10 per cent, solution of chloral hydrate is very suitable for 

 preserving purposes. From teased-out preparations of the retina 



* Arch. f. Mikr. Anat., xxv. (1885) pp. 1-48 (1 pi.). 



t Internat, Monatsschr. f. Anat. u. Histol., i. (1884) p. 225. Cf. Zdtschr. f. 

 Wiss. Mikr., ii. (1885) pp. 396-7. 



