378 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



tilled water, which had a softening and decalcifying effect. This was 

 followed by Schultze's maceration fluid, and afterwards for a few minutes 

 with very strong chromic acid solution. As the objects are brittle, and 

 are rendered still more fragile by the reagents, much care must be taken 

 during the manipulation. After washing out the chromic acid the pre- 

 paration should be stained with a weak solution of Ruthenium red. No 

 definite rule could be given for the action of the various reagents, as 

 the different resistances of the various samples could not be previously 

 estimated. 



Studying the " Islets of Langerhans " in the Pancreas.* — H. H. 

 Dale fixed the pancreas of dog, cat, rabbit, and toad in a mixture of 

 sublimate and formalin. This was made fresh as required by mixing 

 three or four volumes of a saturated aqueous solution of sublimate with 

 one volume of formalin. In some cases sublimate alone was used. The 

 pancreas of dog or cat was cut into thin slices ; the rabbit's pancreas, 

 being spread out into a thin layer in the mesentery, needed no such 

 section ; the toad's pancreas was fixed entire. After an immersion of 

 24 hours the tissue was washed for 24 hours in running water, passed 

 through upgraded alcohols to xylol, and imbedded in paraffin in the 

 usual way. Sections of toads' pancreas were made 5 yu, thick, while those 

 of the mammals varied from 2-4 /m. 



The sections were stained with eosin and toluidin-blue (1 p.c. 

 aqueous solution). The sections, freed from paraffin, were passed from 

 alcohol to dilute tincture of iodine, to remove the sublimate. The iodine 

 was washed out in 60 p.c. alcohol, and after passing through water the 

 sections were stained with eosin. Excess of eosin was removed with 

 ■60 p.c. alcohol, until the zymogen granules could be seen under a low 

 power stained more deeply than the rest of the tissue. The eosin was 

 then fixed with dilute acetic acid, and after washing with distilled water 

 the sections were stained with toluidin-blue. After the ordinary treat- 

 ment the sections were mounted in balsam. 



Fixing and Staining Cells of Embryo-Sac. | — J. Perriraz tried 

 17 different fixatives for his study of the directing spheres in the cells 

 of the embryonic sac. The directing sphere is a term which includes 

 the centrosome, the attraction sphere, and the aster. The author mixes 

 solutions of silver nitrate, and mostly used the following : 1 p.c. osmic 

 acid 4 c.cm., 1 p.c. nitrate of silver 35 can., saturated aqueous solution of 

 picric acid 25 c.cm., absolute alcohol 25 c.cm. The nitrate of silver is 

 first mixed with the water, and then hot picric acid is added, and after 

 this the osmic in absolute alcohol. The mixture is then heated for a 

 few minutes in a water bath at 45°-50°, after which it is allowed to cool 

 in a dark chamber. 



The material is fixed in the dark at from 25°-30°, and then passed 

 through graded alcohols. Then follows a graduated series of alcohol 



* Phil. Trans., Series B., No. 197 (1905) pp. 25-46 (2 pis.). See also this 

 Journal, 1904, p. 296. 



t Bull. Soc. Vaudoise Sci. Nat., xli. (1905) pp. 213-56. 



