FORM AND COLOUR OF THE BLOOD-CELLS. 169 



dark colour of the blood of the portal vein is therefore owing to 

 the quantity of alkali contained in it. 



Notwithstanding the praiseworthy investigations which have 

 been carried on in reference to this subject, and have elicited many 

 facts confirmatory of the above-mentioned views, the study of the 

 changes which the colour of the blood undergoes, in consequence 

 of alterations in the form of the cells, seems still to demand a 

 more searching inquiry. Harless has already made a very pro- 

 mising beginning in reference to this subject. He has examined 

 the influence of gases on the blood-cells, and although he merely 

 experimented on the large, elliptical, biconvex corpuscles of the 

 frog, he has not only confirmed several former observations, but has 

 likewise thrown unexpected light on several points in connexion 

 with this question. Thus for instance, we formerly ascribed to 

 oxygen solely a chemical part in its action on the colour of the 

 blood, although it was known that it could be removed from the 

 blood in a mechanical way, namely, by diffusion in other gases, or 

 by the air-pump ; but Nasse, Scherer, and Harless have obtained 

 actual proofs of the accuracy of Henle's assumption, that both 

 oxygen and carbonic acid give rise to changes in the form of the 

 blood-corpuscles, on which the brighter or the darker redness of 

 the mass of the blood depends. 



Although Miiller did not expect that oxygen and carbonic acid 

 would exert any visible action on the form of the blood-corpuscles, 

 H. Nasse asserted that he had found, from often repeated experi- 

 ments, that the discoid corpuscles of the mammalia become 

 more opaque in their centre by carbonic acid, that the outer edge 

 becomes broader, and that thus the whole vesicle swells, while 

 after the action of oxygen the central depressions of the cells, as 

 wells as their outlines, become more distinct ; and this statement 

 is completely borne out by the observations made by Harless on 

 the blood-corpuscles of frogs ; after the action of oxygen on frogs' 

 blood, he found the long diameter of the corpuscles = 0*011"', the 

 transverse diameter = 0'009"', their form strongly elliptical, their 

 outlines dark, the cell-wall very finely granular, the nucleus of a 

 roundish oval form but not very distinct, and the contents of a 

 pale yellow colour ; while after the application of carbonic acid, the 

 long diameter was increased to G'014'", and the transverse diameter 

 to 0-097'", the form was almost spherical, the capsule as clear as 

 glass, the nucleus distinct and with a sharp outline, and the 

 contents redder than in the previous experiment. 



The simultaneous action of the neutral alkaline salts, and of 



