CHAPTER XXIX. 369 



cent, and brings into acetone, in which fat is dissolved, but not lecithin, 

 which can then be stained by osmium. 



See also CIACCIO, Arch. Zellforsch, v, 1910, p. 235 ; and FISCHLER, 

 Zeit. wiss. Mik., xxii, 1905, p. 262 ; LOISEL, C. E. Soc. Biol., Iv, 1903, 

 p. 703. 



BELL with a modification of DIETRICH'S and CIACCIO'S methods 

 (Journ. Path, and Bad., xix) claimed to be able to distinguish between 

 fat drops mainly of triolein and those that principally contain " lipoids." 

 The former appear in annular shape, the latter are quite solid. In the 

 former case the centre of the droplet is not chromated, and therefore 

 dissolves out in xylol used for imbedding. Fix at 45 C. to 50 C. in 

 10 per cent, aqueous K 2 Cr 2 7 , 100 c.c., acidified by 5 c.c. of acetic. 

 Wash, dehydrate and imbed in paraffin. Fasten 3 to 5 ^ sections to 

 slide with albumen water. Treat sections in xylol, absolute alcohol, 

 and transfer to freshly prepared solution of Sudan III in 80 per cent. 

 alcohol for ten minutes. Rinse off excess stain in 50 per cent, alcohol ; 

 transfer to water to stop action of alcohol. Counterstain in Delafield's 

 hsematoxylin, wash in water, differentiate in acid alcohol, wash and 

 mount in glycerin gum-arabic. 



772. Mounting Fat. After treatment with osmic acid sections can 

 generally be mounted in balsam without special precautions. Many 

 lipoids, however, fade even after osmication, if kept for a long time in 

 balsam. In some cases it may suffice to avoid absolute alcohol and 

 essences as much as possible, and mount direct in alcohol balsam or 

 euparal, or clear with cedar oil, which has little solvent action. For 

 very delicate fats it may be necessary to avoid alcohol of more than 

 70 per cent., or avoid it altogether, and mount in glycerin or levulose. 



Chrysoidin (L. MARTINOTTI, Zeit. Physiol. Chem., xci, 1914) fixes 

 tissue in 10 per cent, formol, sections on a freezing microtome, 

 washes in aq. dest., and immerses for five to ten minutes up to 

 several hours in a 1 per cent, aqueous solution of chrysoidin. Wash 

 not longer than one minute in aq. dest., and treat in 10 per cent. 

 K 2 Cr 2 07 or Cr0 3 for one minute, wash, dehydrate in benzol and 

 xylol, and mount in neutral balsam. 



Bone.* 



773. Bone, Non-decalcified. RANVIER (Traite, p. 297) has the 

 following : 



Bones should be plunged into water, without being allowed to 

 dry, as soon as the surrounding soft parts have been removed, 

 and should be divided into lengths with a saw whilst wet. The 



* For a detailed review of the whole subject, see the paper of SCHAF- 

 FER in Zeit. wiss. Mik., x, 1893, p. 167, or the article " Knochen und 

 Zahne " in Encycl. mile. Technik. 



| This section has been revised by J. Thornton Carter, Esq., 

 F.R.M.S., of the Zoological Department, University College, London. 



M. 24 



