168 BLOOD. 



induced in the colour of the blood by (chemically speaking) very 

 indifferent substances, as, for instance, sugar and neutral alkaline 

 salts, soon led observers to support Henle's view, and amongst 

 them we must name one of the first of our heematologists, 

 H. Nasse. If we dilute blood with water, it assumes a dark red 

 colour ; if the blood were previously dark-coloured, it becomes still 

 darker on the addition of water ; if, in these cases, we examine the 

 blood-corpuscles under the microscope, we find them distended, and 

 observe that they have almost lost their discoid form and become 

 spherical; the blood collectively must therefore appear darker, 

 since each individual corpuscle has become converted into a 

 spherical mirror, from which the red rays are scattered and reflected. 

 We observe the reverse on treating the blood with neutral salts, 

 syrup, or in short, any such substances as render the intercellular 

 fluid relatively denser : a diffusion-current is established from the 

 cells towards the intercellular fluid, in consequence of which, the 

 former must collapse. A microscopic examination shows us that the 

 collapse of the corpuscles by exosmosis causes the central depres- 

 sion to become more considerable, and the individual cells to 

 resemble concave mirrors. It is believed that the lighter colour of 

 such blood must be referred to the reflection of the red rays. 



Scherer,* who has very carefully studied this influence of the 

 form of the cells on the colour of the blood, indicates also another 

 physical cause, which exerts an influence on its coloration. 

 The change in the form x>f the cells must be accompanied by a 

 thickening or an attenuation of the investing membrane. It 

 is obvious that when the capsule becomes thinner by the expansion 

 of the blood-corpuscles, the pigment must shine through more in 

 its natural, that is to say, its dark red colour, and consequently, 

 must impart a dark coloration to the mass of the blood ; and that 

 when the corpuscles are diminished, their capsules must become 

 thickened or thrown into folds, and must thus to a certain degree 

 conceal the true colour of the hsematin. In a somewhat similar 

 manner, Mulder believes that the reason why arterial appears of a 

 lighter red colour than venous blood, is, that the corpuscles of the 

 former are surrounded by a dense layer of binoxide of protein, 

 while those of the latter possess a thinner investing membrane. 

 Hence Mulder agrees with von Baumhauer in the belief that 

 alkalies and dilute mineral acids communicate a dark colour to the 

 blood, since they swell up the investing membrane, which is rich in 

 binoxide of protein, and thus render it more transparent 5 the 

 * Zeitschr. f. rat. Med. Bd. 1, S. 288. 



