332 PROCEEDINGS OF THE ACADEMY OF [May, 



demonstrated by this stain (namely, two to three minutes in a 7-15 

 per cent, sokition in aniline water) always exhibit the blackened 

 granules only. In fig. 10, Plate XVI, some small red granules are 

 seen near the free edge of the cell ; these may be due to the small 

 amount of proteid in the boiled potato with which the olive oil was 

 mixed, or may represent small globules composed in part only of fat. 

 Thirdly, the final test of fats is always the action of fat solvent 

 — ether, xylol, benzole, etc. After most fixations, as is well 

 known, fat is easily dissolved out by prolonged immersion in xylol or 

 ether. 



Thus the intestine from an animal known to have eaten only fat 

 after a starvation of one week was fixed after twenty-one hours, 

 first in 1 per cent, platinic chloride, washed in water and carried 

 through the alcohols in the usual way to harden. Instead of im- 

 bedding at once, it was subjected to the solvent action of xylol for 

 forty-eight hours. On sectioning and staining in acid-fuchsine no 

 blackened globules were found in any of the cells. 



But after osmic acid fixations the authorities are not agreed as to 

 the solubility of fats in the ordinary solvents. Heidenhain (29) 

 argued that certain black granides in the absorbing cells of mam- 

 malian villi and in the lymph corpuscles were not fat l)ecause they 

 did not dissolve in xylol and ether, and on this fact he based cer- 

 tain far-reaching conclusions. Altmann (30), however, and Moore 

 in Schafer's Text-book of Physiology (Vol. I, p. 458, note 5), state 

 that prolonged treatment with osmic acid tends to render fat in- 

 soluble. This I can confirm from the following experiment con- 

 cerning fat globules in cells : 



Intestines from animals which ate butter for eight minutes after 

 a starvation of one week, fixed in Hermann's fluid without acetic 

 acid after sixteen hours and treated with xylol, exhibit abundant 

 blackened granules. In one case (fig. 18) the intestine was fixed in 

 Hermann's fluid, and after the sections were moimted one of the 

 slides of the series was sketched with the camera while in oil of 

 cedar in preparation for balsam. The position of every globule in 

 the cell was noted. It was then placed in ether over night (fifteen 

 houi-s) and was again examined in oil of cedar. No change in the 

 globules had taken place. The slide was then placed in benzole for 

 four or five hours and again carefully examined ; no globules had 

 dissolved, although the color had faded noticeably. There is no 

 possibility of confusion with albumose granules in this case, as the 

 animal was carefully isolated for nine days before feeding and was 

 then allowed to eat onlv butter for ten minutes. It was killed and 



