120 



BLOOD-CRYSTALS. 



in 600 parts of water, the prismatic 

 in 90 parts only; the solution in 

 the former case being pinkish, that 

 of the latter, dark red. They are 

 also dissolved by acetic acid, the red 

 prussiate of potash producing a pre- 

 cipitate therefrom, as in the case of 

 ^ other protein bodies. Chlorine de- 

 colorizes their solutions and gives a 

 white flaky precipitate. The crys- 

 tals, when heated, swell, yield an 

 odor like burnt horn, and, after com- 

 bustion, leave a small quantity of 

 Biood-crystais of squirrel. as h. From the difficulty of obtain- 



ing blood-crystals in a state of purity, their constitution is not known 

 with absolute certainty. The ash which they yield consists of about 72 

 per cent, of oxide of iron, and 21 per cent, of phosphoric acid, the protein 

 constituent being apparently identical with other protein bodies. The 

 Mode of ob- crystals may be obtained for examination by covering a mi- 

 taining blood- nute drop of blood with a glass slide, and, after adding water, 

 alcohol, or ether, to permit a gradual evaporation to ensue. 

 The amount thus produced depends very much upon the presence of light; 

 thus Lehmann found that while he could only obtain two per cent, of 

 crystals from the blood of the Guinea-pig in the dark, he could obtain 

 more than seven per cent, in the sunlight. 



Lehmann believes that the crystalline substance is not a mixture of a 

 pigment and a protein body, but a pure chemical compound, having either 

 a salt-like or conjugated constitution. 



The color of the blood, as dependent upon the tint of its cells, is, ac- 

 Coior of blood- cording to the views of Henle, connected to a considerable 

 degree with the form of those organisms as they vary from a 

 concave to a convex surface, and not with the state of the 

 hsematin. When they are more concave they are of a crimson, when 

 of a more convex, of a darker hue. Moreover, during these variations 

 their investing membrane must necessarily change in thickness, and this 

 likewise must alter their mode of transmitting light. 



Among the causes which can impress a change on the figure of the 

 blood-cells ought particularly to be specified exposure to oxygen and 

 carbonic acid respectively, the latter causing them to become more opaque 

 in their centre, broader upon their edge, the cell distending ; an opposite 

 effect ensuing under exposure to the former. In the case of the blood- 

 cells of frogs exposed to oxygen, the long and short diameters both di- 

 minish, and the wall becomes granular ; after exposure to carbonic acid 

 they increase, the wall becoming pellucid. 



cells may de- 

 pend on their 

 form. 



