184 BLOOD. 



coagulation of the blood. Denis and Lecanu have attempted to 

 demonstrate the presence of fibrin in the blood-corpuscles by 

 triturating them with salts, viz., nitrate of potash and chloride of 

 sodium; Virchow, who has repeated these experiments, has however 

 shown that the small membranes observed by these authors are 

 nothing more than the folded and adhering walls of the blood- 

 corpuscles, which, under the microscope, in consequence of the 

 pressure and the crushing of the glass covering the object, often 

 acquire the appearance of Nassers fibrinous flakes ; Virchow, how- 

 ever, very correctly remarked that the solubility of these mem- 

 branes in a solution of nitre, and their swelling in acetic acid, by 

 no means prove their identity with fibrin : moreover I was unable 

 to obtain a trace of coagulable matter, or of matter precipitable by 

 acetic acid, from the cell-membrane of the corpuscles of the blood 

 of horses and oxen by prolonged digestion with a solution of nitre. 

 Mulder regards the cell-wall as binoxide of protein; but the 

 properties of the remains of the cell-walls obtained by treating 

 blood with water by no means coincide with those of Mulder's 

 binoxide of protein ; they are far more difficult of solution in 

 acetic acid and in the alkalies than the latter ; and in these mem- 

 branes I have not been able to detect any trace of sulphur, which, 

 as is well known, is contained in binoxide of protein. Moreover, 

 Mulder has not demonstrated the presence of this substance by 

 direct experiments, but was merely led to this view by the following 

 consideration : on their passage through the pulmonary capillaries, 

 the blood-corpuscles become invested with a thicker layer of this 

 binoxide, in consequence of which the blood-pigment appears of a 

 lighter red colour, as if seen through ground glass, and hence the 

 lighter red tint of arterial blood ; the central depression of the 

 coloured cells also bears out this view, since the inflammatory crust 

 in which, as is well known, there is much binoxide of protein, has 

 also a great tendency to exhibit a similar depression or concavity. 



It is very probable that the cell-walls of the corpuscles even 

 of the same blood have not a precisely identical composition; at 

 all events we see that the coloured cells of the same blood are, as 

 a general rule, very unequally acted upon by the same reagents ; if, 

 for instance, we allow water, dilute acids, ether, or dilute alkaline 

 solutions, to act on the blood-corpuscles, we perceive that the work 

 of destruction does not by any means proceed uniformly ; thus 

 some do not disappear even when the blood is very much diluted 

 with water ; these we consider to be the younger cells, while those 

 which are easily destroyed are regarded as the older blood-corpuscles ; 



