178 BLOOD. 



That the bicarbonate of potash is converted in the blood of 

 living animals into carbonic acid and simple carbonate or sesqui- 

 carbonate of potash, is also obvious from experiments which I have 

 made with frogs. These animals were placed in differently satu- 

 rated solutions of bicarbonate of potash or soda, and were fixed in 

 such a manner that they could breathe freely, and that the web- 

 membrane of one foot could, at the same time, be observed under 

 the microscope. Within three minutes after the beginning of the 

 experiment, the blood-corpuscles began to accumulate in the 

 smaller capillaries of the web-membrane, while in the larger 

 ones there was as yet no perceptible diminution of the rapidity of 

 the circulation; in from 10 to 15 minutes, however, temporary 

 accumulations and short stoppages were perceptible ; at a still later 

 period an oscillation began in these larger vessels, so that it was 

 no longer possible to distinguish in which direction the current 

 was running. As far as was possible, the blood-corpuscles of this 

 frog were compared with those of another (not exposed to the 

 action of a salt), whose web-membrane was simultaneously brought 

 under another microscope of nearly the same magnifying power. 

 Nuclei, which, as is well known, are not generally perceived in the 

 blood-cells of frogs 3 blood in the act of circulation, here also could 

 not be recognised ; but although accurate measurements of the 

 blood-cells within the web-membrane could not be made, yet 

 a comparison of the blood-cells in the two kinds of circulating 

 blood, showed (after a condition of stasis had commenced in the 

 finer capillaries of the web-membrane of the frog placed in the salt), 

 that the corpuscles of the blood in which the alkaline bicarbonate 

 was diffused, were swollen, shortened in their long diameter, and 

 diluted transversely. These phenomena and alterations in the 

 dimensions of the blood-corpuscles were even more distinct in frogs 

 which were gradually suffocated in an atmosphere rich in carbonic 

 acid. 



In both cases, the blood of the larger vessels and of the heart 

 was not of a brownish red, but of a purplish colour, merging from 

 a cherry red into an almost perfect violet ; the blood-corpuscles 

 without a decided nucleus, exhibited a central and peripheral turbid- 

 ity, independent of the arrangement of the microscope; some were 

 enlarged in diameter and volume. On the addition of bicarbonate 

 of potash to the blood of the frog treated with carbonic acid or the 

 alkaline bicarbonate, the fluid exchanged its purple colour for a light 

 vermilion tint ; the blood-cells were, however, so contracted that 

 when seen under the microscope they resembled crumpled elliptic 



