CYTOLOGICAL FIXING AGENTS. 333 



tions of 1 300 strength. Platiuum chloride has the pecu- 

 liarity of causing a slight shrinkage of the chromatin, which 

 helps to bring into evidence the granules of Pfitzner and the 

 longitudinal division of the chromosomes. 



There remain to be mentioned several fixing agents with which very 

 important work has been done. These, however, are, I think, not quite first- 

 class reagents for the purpose, the brilliant results that have been obtained 

 with them having been obtained rather in spite of their defects than on 

 account of their good qualities. For instance, acetic alcohol is a reagent 

 with which some of the most important work in recent cytology has been 

 done namely, much of that on the maturation and fecundation of the ovum 

 of Ascaris. It is evident that for such an extraordinarily impenetrable 

 object as the ovum of Ascaris, the employment of some such highly pene- 

 trating fluid as acetic acid is imperatively indicated, notwithstanding certain 

 defects that it may have. 



CAKXOY (La Cellule, iii, 1, 1886, p. 6) used at first a mixture of three 

 parts of absolute alcohol with 1 of glacial acetic acid ; later (ibid., iii, 2, 1887) 

 the chloroform mixture ( 54). From five to fifteen minutes is enough for 

 even the most resistent ova. 



VAN BENEDEN and NEYT (Nouvelles Eech. sur la Fee. et la Division 

 mitosique, 1887) employed a mixture of equal parts of absolute alcohol and 

 glacial acetic acid, or even pure acetic acid. 



Acetic alcohol may be washed out with either pure alcohol, or with dilute 

 glycerin (Calberla's formula would be a good one in many cases). For 

 further details see ante, 54 



M. HEIDENHAIN (Ueb. Kern u. Protoplasma, 1892, p. 113) has been 

 using corrosive sublimate, on account of its convenience, and, above all, on 

 account of the great facility it affords for the employment of any kind of 

 stain. The beautiful figures of attraction spheres and other cytoplasmic 

 structures given in this paper show that the most brilliant results may be 

 obtained by this means. But I would remark that the figures of nuclear 

 structures appear to me less convincing. The author figures and describes 

 under the name of " Lanthanin," an acidophilous caryoplasmic substance ex- 

 hibiting a minutely reticular arrangement. The figures remind me of 

 appearances which I frequently obtained in certain nuclei when working 

 with sublimate some years ago, and which I regarded as artefacts, and in 

 consequence was led to the abandonment of sublimate as a cytological fixa- 

 tive. I do not find in Heidenhain's paper that he has instituted control 

 experiments to show that the reticular arrangement of his " lanthanin " is 

 preformed in the nucleus, and would point out the need of such experiments 

 before either the existence of the lanthanin reticulum or the fidelity of the 

 reagent can be deemed established. 



ALTMANN (Arch.f. Anat. u. EntwicJcel, 1892, p. 223 ; Zeit. f. wiss. Mik., 

 ix, 3, 1893, p. 331) has a new fixative for resting nuclei, viz. a 2'5 per cent, 

 solution of ammonium molybdate to which is added about 0'25 per cent, of 

 chromic acid. I have no personal knowledge or other information concern- 

 ing this method. 



