146 SUMMARY OF CURRENT RESEARCHES RELATING TO 



(2) Preparing 1 Objects. 



Preparing Ova of Amphibia.* — Dr. O. Schulze places tho ova of 

 amphibia (tho investment derived from the oviduct having been removed) 

 for twenty-four hours iri chrom-osmium-acetic acid, or in chrom-acetic 

 acid, and then Avashcs them well with distilled water. At tbis point 

 they are available for surface study. They are next immersed every 

 twenty-four hours in spirit of 50, 70, 85, and 95 per cent., the latter 

 being changed several times. Next in turpentine for one to two hours, 

 according to tbe size of tho ova. They are then transferred to paraffin 

 (50°), whereof they have sufficiently imbibed in a half to one hour. It 

 is noted tbat the time given must be carefully observed. The sections 

 were fixed to the slide with some thin adbesive, and then after evapora- 

 tion of the water treated in tbe ordinary way. Borax-carmine was used 

 as the stain, and decoloration effected with acidulated 70 per cent, spirit 

 ( 5 drops HC1 to 100 c.cm.). By frequent change of this tho yolk-granules 

 were decolorized, and only the chromatic substance remained red. 



Chrom-osmium-acetic acid cannot be used for fixing substances lying 

 centrally in the egg. 



Preparing Testicle for observing Nuclear Fission.j — Dr. W. Flem- 

 ming's recent examination of cells was made on the testicle. The organ 

 was very rapidly teased out on a slide, and the fixative dropped over it. 

 Chrom-acetic-osmic acid five times diluted or Brass's mixture for Protozoa, 

 used rather strong, were the media employed for fixing. The prepara- 

 tion having been repeatedly wetted with this fixative was transferred to 

 a moist chamber for several hours ; the preparation was thereby hardened 

 on the slide, and bore washing with a gentle stream of water for half an 

 hour. Staining was performed by dropping on a safranin or gentian solu- 

 tion, and then allowing the slide to stand in the moist chamber for some 

 hours. The preparation was then washed, and dehydrated with absolute 

 alcohol, to which a trace of hydrochloric acid was added if the osmium 

 mixture had been used for hardening. 



The advantages of this method are that the cells lie pretty close 

 together, and are often very beautifully stained. On the other hand, 

 the nuclear figures may be destroyed by the teasing, and the contents of 

 various cysts are so commingled that the various stages of fission cannot 

 be compared. For making sections the testicles were placed in strong 

 osmic acid. Then prolonged and careful saturation with celloidin, for 

 the capsule after hardening in osmic acid is penetrable with difficulty. 

 Sections were stained with gentian or safranin. Haematoxylin was fairly 

 successful, but the nuclear staining was rather dull. Kemoval of the 

 celloidin improved the clearness of the pictures. For this purpose the 

 section was first treated with bergamot, and this having been removed 

 by drainage and bibulous paper, was replaced by oil of cloves, which 

 gradually dissolved the celloidin. Then dammar. Before cutting, the 

 lobule of the testicle was examined for evidence of nuclear fission ; if 

 found it would be present in the other lobules. 



Demonstrating Cell-granules.J — Dr. E. Altmann demonstrates cell- 

 granules in the following manner : — The paraffin sections, stuck on mica- 

 scales with alcohol in which a little gun-cotton is dissolved, are freed 



* Zeitschr. f. Wiss. Zool., vi. (1887) pp. 177-226 (3 pis.), 

 t Arch. f. Mikr. Anat.. xxix. (1887) pp. 389-463 (4 pis.). 

 X ' Sludien iiber die Zellc.' 1886, Heft 1, 53 pp., 1 pi. 



