SOME OTHER HISTOLOGICAL METHODS. 437 



788. Adenoid Tissue. See HOEHL, Arch. Anat. Phys., Anat. Abth., 

 1897, p. 133 ; Zeit. f. wiss. Mik., xv, 1898, p. 228. 



789. Fat. DEZHUYSEN and FLEMMING (Zeit. f. wiss. Mile., 1889, 

 pp. 39, 178) have discovered that fat that has been stained black by treat- 

 ment with chromo-aceto-osmic acid is dissolved in the course of a few hours 

 in turpentine, xylol, ether, or creasote, and more slowly if it has been 

 blackened with pure osmic acid, and FLEMMING finds that very good 

 demonstration preparations may be made by treating fatty tissue with 

 chromo-aceto-osmic acid, staining with safranin or gentian, and then 

 treating for a few hours with turpentine until all the fat is dissolved. The 

 optical hindrance caused by the high refraction of the fat being thus 

 eliminated, nuclei and cytoplasm may be studied to far greater advantage 

 than in the usual preparations. See also 36, sub fin. 



790. Sudan III Stain for Fat. DADDI (Arch. Ital. Biol., 

 xx vi, 1896, p. 143) stains fat in tissues by treating for 5 to 

 10 minutes with concentrated alcoholic solution of Sudan 

 III, washing for the same time with alcohol, mopping up 

 with blotting-paper, and mounting in glycerin (the speci- 

 mens can hardly be mounted in balsam on account of the 

 solution of the fat in the absolute alcohol, etc.). Small fat 

 drops yellow, large ones orange. The stain is said to be 

 more selective for fats than that of osmic acid. 



Similarly RIEDER, see Zeit. f. wiss. Mik., xv, 1898, p. 

 211. 



791. Granule cells, " Mastzellen," " Plasmazellen," and others. 

 For the general characters of these cells, and for EHELICH'S classification of 

 granules, see previous editions. I am now much inclined to doubt the 

 objectivity of Ehrlich's classification, for the reasons assigned by FISCHEB 

 in his Fixirung, Fdrbung u. Bau des Protoplasmas, which see. 



792. EHRLICH'S "Mastzellen" (Arch. f. mik. Anat., xii, 

 1876, p. 263). The tissues must be first well hardened in 

 strong alcohol (chromic acid and its salts must be avoided). 

 They are then placed for at least twelve hours in a staining 

 fluid composed of 



Absolute alcohol . . . 50 c.c. 



Aqua .... 100 c.c. 



Acid. acet. glacial . . . 12^ c.c. 



to which has been added enough dahlia to give an almost 

 saturated solution. After staining, the preparations are 

 transferred to alcohol, which washes out the stain from all 



