460 SUMMARY OF CURRENT RESEARCHES RELATING TO 



about twenty minutes, when bands of section • 005 mm thick can be 

 easily cut. The advantages of this method are a good hardening and 

 coloration hrst, and a consequent preservation of all parts of the series 

 of sections. 



1, ,^^^«ii^i»gr the Central Termination of Optic Nerve in Verte- 

 brata.^— For tracing the course of nerve-fibres the following has been 

 employed with great success by Prof. J. Bellonci :— 



^^^ TJ^eJjrain or a part containing the nervus opticus is placed in 

 osmic acid (1/2 to 1 per cent.) for fourteen to twenty hours 



(2) Freehand sections are then made in 70 per cent, spirit The 

 sections are washed in distilled water for a few minutes, and then'placed 

 m 8U per cent, spirit for three or four hours. 



f ^^^^I'f sections are again placed in distilled water, and then trans- 

 lerred to the slide and the cover-glass put on. 



(4) A few drops of ammonia are then allowed to mix with the water 

 under the cover-glass. This reagent makes the brain as transparent as 

 glass, except the nerve-fibres, which remain black, and which are brou-ht 

 out with such distinctness that their course is easily followed 



The sections are of course thick, but this is an advantage in tracing 

 the winding course of the nerve-fibres. Sections cut in celloidin with 

 tfie microtome can be treated in the same manner, but the action of 

 tne ammonia is then much slower, requiring several days. 



Preserving: Nervous Systems.f-Mr. A. Sanders has been examining 

 the nervous system of Ceratodus Forsteri in the wild parts of Queensland^ 

 He adopted a method of treatment to which the nervous system was sub: 

 jected before molecular death could take place. The head immediatelv 

 after it was cut off. was placed in Miiller's' solution to whlraTcott 

 the proportion of one-third had been added; the solution was changed 

 next day, and wo or three times in the course of the succeeding three 

 weeks. The skull containing the brain was then placed in a 2 pfr cent 

 solution of potassium bichromate, which was changed once a fortnight 

 until the brain was sufficiently hard to be cut into sections. ThisTccurs at 

 various periods taking a shorter time in the higher Vertebrates than in 

 the lower ; m the case of Ceratodus the period Sas longer than a year 

 Mr. Sanders has always found this method to succeed well, and thinksTt 

 IS of great advantage when there is no opportunity of cu'i^g sections 

 till some time after the capture of the animals, and\e " can rfcommend 

 It as an all-round method for travellers." iccommena 



Investigation of Ova of Sepia.J-M. L. Vialleton fixed the ova of 

 Sepia with osmic acid and Kleinenberg's picrosulphuric mixtu.l After 



wo days they were placed in 70 per cent alcohol, which was rentwed 

 till all colour was removed, and they were then stained wiS carmrne 

 and cut into sections To isolate the protoplasmic layer the ova were 

 placed in a mixture of equal parts of Kleinenberg's fluid and a 2 5 per 

 cent, solution of bichromate of potash. This immediately hardens the 

 chorion and a lows of its being easily separated from^the yolk • he 

 S.'l . "'* 'Tr^ ^'' "^^^-^ than one or two minutes The; Ire 



hen placed m a watch-glass containing Kleinenberg's fluid in such a Wav 

 that the protoplasmic layer looks upwards. At th^e end of an hour Ind 



* Zeitschr f. Wiss. Zool., jlvii. (1888) p. 4 

 t Ann. and Mag. Nat. Hist., iii. (1889) p. 158. 

 X Ann. Sci. Nat., yi. (1888) pp. 168-71 



