332 CYTOLOGICAL METHODS. 



general work. Whether of these two solutions should be 

 used for general work ? According to my experience, the 

 strong solution does preserve both nuclear structures and 

 caryoplasmic structures quite as faithfully at least as the old 

 formula, and some structures most decidedly much better. 

 Of course the one and the other should be taken according 

 to the nature of the object you are dealing with ; but I think 

 it may safely be stated as a general rule that if you take the 

 strong mixture, and fix thoroughly in it, you are not likely to 

 go far wrong. And what is meant by a thorough fixation ? 

 Half an hour may be taken to be generally enough ; but for 

 very delicate things, such as the Nebenkern. and the achro- 

 matic figure, at least eighteen hours ought to be given. 



It only remains to point out that this doctrine is at variance 

 with that expressed in the first edition and in the Traite, and 

 with the earlier recommendations of Flemming ; but I feel 

 some confidence that it will not be called in question by the 

 majority of workers at this subject. Of course it goes without 

 saying that further precise evidence on the matter is very 

 much to be desired. 



As to the platino-aceto-osmic mixture of HERMANN, it has 

 already been explained in 51 that the point of superiority 

 over Flemming's mixture that is claimed for it lies in a more 

 faithful preservation of cytoplasm and achromatic structures. 

 That the alleged superiority really exists appears to be the 

 general opinion of those who have worked with this reagent. 

 Flemming (Arch. f. mik. Anat., xxxvii, 1891, p. 685; Zeit. f. 

 wiss. Mik., viii, 3, p. 343) agrees that it gives a peculiarly 

 sharp demonstration of spindle fibres, centrosomes, and polar 

 corpuscles ; but thinks that the chromo-aceto-osmic mixtures 

 give a somewhat more faithful preservation of the chromatic 

 elements. 



Two or three of the fixing agents proposed by other writers 

 may also rank as first-class reagents for this kind of work. 

 There is RABL'S chromo-formic acid ( 32). Fix in this for 

 twelve to twenty-four hours, wash out well with water, and 

 pass into alcohol. And there is the same observer's platinum 

 chloride solution ( 50). In Babl's paper in Anat. Anz., iv, 

 1889, p. 21, he recommends that Salamandra larvse be fixed 

 (for twenty-four hours) in a solution of from one tenth to one 

 eighth per cent, strength. In his earlier work he used solu- 



