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exist on them ; but also with a view to the questions for the solu- 

 tion of which the red blood-cells are not serviceable, because they 

 are known to lose their colouring matter very easily. 



For yeai's then it had been my desire to extend my researches in 

 the above direction, yet, extremely simple as my plan was in prin- 

 ciple, I was checked by the difficulty of obtaining a sufficient quantity 

 of isolated cells, which, with the means, then at my disposal, would 

 have enabled me to determine their volume. 



This difficulty has now been overcome by the use I can make of 

 little tubes which I constructed last year to compare the volume of 

 bacteria in two cultures, and which admit of experiments with 

 small quantities '). We have, as yet, investigated four sorts of cells, 

 white and red corpuscles of different animals, spermatozoa of the 

 frog and the intestinal epithelium of the horse and the pig. 



We shall treat of the intestinal epithelium on some future occasion. 



Phenomena of a peculiar natui-e, which have manifested themselves 

 while studying it, make a further research necessary. 



White blood-corpuscles. 



These were obtained by leaving horse-blood, in a closed bottle 

 defibrinated with pieces of glass. The red corpuscles then for 

 the greater part precipitate, while the white all remain suspended 

 in the fluid above. Their number is comparatively small. Now in 

 order to obtain a fluid abounding in white blood-corpuscles, V2 L- 

 of turbid fluid was centrifugalized, 470 cc. of the clear serum 

 eliminated and the precipitate equally divided in the remaining 

 fluid. Of this fluid about V'4 c.c. was measured off' and placed in 

 test-tubes with 15 c.c. of different salt solutions. After repeated 

 mixing, and after half an hour or a little longer 5 cc. or more 

 were placed in the above mentioned little funnel-shaped tubes and 

 centrifugalized till (the rapidity of revolution of the centrifuge not 

 varying) the level remained constant for fifteen minutes. 



1) Beport of tlie meeting of the Hoyul Academy of Sciences, April 21st 1S97. 



i 



