ZOOLOGY AND BOTANY, MICBOSCOPY, ETC. 1041 



200 gr. ; sodium chloride 1 gr. ; sulphate of soda 5 gr. ; perchloride of 

 mercury 0*5 gr. ; glycerin 28°. 



The chief objections to mercurial solutions are, according to the 

 author, that they do not prevent all the corpuscles from becoming 

 altered, and that they always produce a decoloration of the red 

 corpuscles. 



Osmic acid used in 1 per cent, solution preserves blood-corpuscles 

 better than any other known reagent, and does not precipitate the 

 albumen like sublimate. It fises the leucocytes in their natural condi- 

 tion, and though they become granular, they remain transparent, and 

 preserve their proper and characteristic outlines. 



Preserving Blood-corpuscles for Microscopical Examination.* — 

 The following method of preparing permanent microscopical sj)ecimens 

 of blood-corpuscles is extremely simple, and in Mr. R. Leigh's hands 

 has yielded very satisfactory results. 



A thin film of blood on a cover-glass is gently dried, and inverted, 

 for half an hour or more, into a covered capsule containing a half- 

 saturated solution of safranin in absolute alcohol. The loosely adhering 

 stain is then washed off by a stream of distilled water, after which the 

 specimen is again thoroughly dried, and mounted either in Canada 

 balsam, liquefied by heat, or thinned by turpentine. 



With human blood the corpuscles are stained a beautiful clear pink 

 colour, and in non-mammalian blood the nuclei are stained dark pink, 

 while the rest of the red corpuscles are lightly tinged. The specimens 

 which were made three months before have retained their colour 

 perfectly. 



Methods for Investigating the Structure of the Central Nervous 

 Organs in health and disease.f — In his ' Introduction to the Study of 

 the Structure of the Central Nervous Organs in health and disease,' Dr. H. 

 Oberstein recommends the dissociation method of Stilling. Harden in 

 Miiller's fluid, and then place in absolute alcohol. Then immerse in 

 artificial wood vinegar for several weeks (glacial acetic acid 200 gr., 

 water 800 gr., kreosote 29 drops). The preparations can, after being 

 treated with oil of cloves, be mounted in balsam. If continuous series 

 of sections be required, the tissue should be hardened in bichromate of 

 potash. Begin with a 1 per cent, solution, change very often, gradually 

 strengthening to 2 or 3 per cent, (time 6-8 weeks). In an incubator at 

 from 35°-45° hardening is effected in 8-14 days. Special care is 

 necessary for hardening spinal cord. If the preparations are to be kept in 

 the bichromate solution after having been hardened, the strength should 

 be • 1 per cent. Hardening may be hastened by the addition of 20 to 

 30 drops of a 1 per cent, solution of chromic acid to the solution of 

 the salt. When hardened the preparations are to be washed and then 

 transferred to 50 per cent., and finally to 95 per cent, spirit. Miiller's 

 and Erlitzki's fluids and bichromate of ammonia are condemned. The 

 best fixative for the delicate structures is a modification of Flemming's 

 solution (Fol): — osmic acid 1 per cent., 2 vols.; chromic acid 1 per 

 cent., 25 vols. ; acetic acid 2 per cent., 8 vols. ; water 68 vols. After 

 being in this fluid for 24 hours, the pieces are thoroughly washed and 

 then placed in 80 per cent, spirit. 



* Journ. Anat. and Physiol., xxii. (1888) p. 497. 



t 8vo, Leipzig u. Wien, 1888, 406 pp. 178 figs. Cf. Zeitschr. f. Wiss. Mikr. 

 V. (1888) pp, 203-7. 



