ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 871 



ferred to the chromic acid solution for 30-40 m". They are then 

 returned to absolute alcohol for 30 or 40 ra", where their colour 

 is somewhat diminished. In order to fix the colour better in the 

 figures it is well to return the sections for 30 m" to the chromic 

 acid solution and then back again to absolute alcohol for 30-40 m''. 

 This done, they are passed into oil of cloves, which extracts more 

 colour. The author states that his experience is that oil of cloves 

 exerts less influence on the nuclei in fission than those in repose. 

 Consequently he uses oil of cloves as long as the colouring matter is 

 extracted, in preference to alcohol which acts on both kinds of nuclei 

 alike. 



Better results are sometimes obtained by combining the effects of 

 the two solutions. The procedure is then as follows : — 5 to 10 m' 

 in the Ehrlich stain ; wash for 5 m" in absolute alcohol ; 2 m' in 

 the iodine solution ; 20 m" in the chromic acid solution ; 15 m" in 

 absolute alcohol ; then 30 m" in the chromic solution ; 30 m" in 

 absolute alcohol ; repeated washing in oil of cloves until the section 

 is only faintly coloured ; then dammar. The latter method is more 

 suitable for examining nuclei of the liver, salivary glands, kidney, 

 and pancreas ; the former answers well with lymphoid tissue. 



The preparations should be examined with an Abbe condenser 

 without a diaphragm or with a very large one. In successful pre- 

 parations the cell protoplasm is uncoloured, and in the nuclei in 

 repose only the faintly stained nucleoli are to be seen, while the 

 figures are a deep, almost brown, violet. 



Preparations which have been hardened in chromic acid or in 

 chrom-osmio-acetic acid stain well by this method if the sections are 

 well washed in alcohol. • 



Reagents for studying the Structure of Gland-cells.* — 1. Chro- 

 mic acid. — Dr. J. H. List uses this as a 0*1 per cent, solution for 

 eight days when needed for isolation hardening. When required for 

 sections a 1/4 per cent, solution is used for three days ; the speci- 

 mens are then thoroughly washed, and having been hardened in 

 alcohol to dehydration, are imbedded in celloidin. They are then 

 stained with anilin, e. g. Weigert's Bismarck brown, rosanilin nitrate, 

 and dilute Benaut's haematoxylin-glycerin. Sections made by this 

 method show the structure of gland-cells (both goblet and mucous 

 cells) excellently. 



2. MiiUer's fluid. — This imparts the requisite hardness in a week 

 or so ; the specimens having been soaked for twenty-four to forty- 

 eight hours, the isolated elements may be stained with methyl-green 

 (1 per cent.), anilin-green (1 per cent.), or rosanilin nitrate. When 

 sections are required, after the MiiUer's fluid the pieces are soaked 

 and then hardened in alcohol, imbedded in celloidin, and then stained 

 as before (No. 1). 



3. Osmic acid. — This is used as a 0*5 or 1 per cent, solution. 

 Small pieces of tissue are left in the 1 per cent, solution twelve to 

 twenty-four hours; in 0*5 per cent, solution twenty-four to forty- 



* Zeitschr. f. Wiss. Mikr., ii. (1885) pp. 514-G. 



