CHEMICAL EXAMINATION OF THE BLOOD. 327 



it begins only after a quarter of an hour. In the horse, in which 

 coagulation is likewise delayed, the corpuscles of the blood have time 

 to settle and form two distinct layers the red at the bottom and the 

 white on top, where they appear as a grayish-white zone, and con- 

 stitute the so-called crusta pklogistica or inftammatoria. Above this 

 we then see the plasma, which has undergone coagulation, and on 

 top of it the serum that has been squeezed out from the clot. The 

 same phenomenon may be observed in human blood when cooled to 

 about C., and from the extent of the crusta phlogistica in such 

 blood the older physicians were wont to draw prognostic conclusions 

 as to the course of the disease. 



The rapidity of coagulation can be artificially increased and 

 diminished. By beating the blood, by increasing its temperature 

 a little beyond that of the body, and by diluting with water it is 

 increased ; while exposure to a low temperature, the presence of 

 much carbon dioxide in the blood, the careful lubrication of the 

 vessel with vaselin or similar unguents, cause a retardation of coagu- 

 lation. Its prevention finally may be brought about through influ- 

 ences already mentioned, viz., by salting with the neutral salts, 

 following the previous injection into the body of albumoses or of 

 histon, of diastatic ferments, of extracts of the mouth-parts of the 

 leech, after elimination of the intestinal bloodvessels by ligation, etc. 



The Red Corpuscles. 



The red corpuscles of the blood, as has been mentioned, owe their 

 color to the presence of haemoglobin or its oxygen compound, oxy- 

 haemoglobin. This may be extracted by diluting with water, by 

 alternate freezing and thawing, by shaking with ether, chloroform, 

 etc. The blood is thereby rendered lake-colored, and on microscopi- 

 cal examination it will be observed that instead of the original cor- 

 puscles, so-called blood-shadows are now found. These are colorless 

 ring-like bodies, and constitute the stroma of the red corpuscles. 

 In the circulating blood the dissolution of the haemoglobin is pre- 

 vented by the presence of large amounts of sodium chloride. Such 

 blood is said to be hyperisotonic i. e., it contains more sodium 

 chloride than is necessary to prevent the dissolution of the coloring- 

 matter from its corpuscles. Within the corpuscles the haemoglobin 

 is, however, supposedly not present in the free state, but in com- 

 bination with some other substance, such as lecithin ; arid Hoppe- 

 Seyler accordingly distinguishes between the so-called arterin and 

 phlebin, which represents the lecithin compound of oxy haemoglobin 

 and haemoglobin respectively. 



As has been mentioned, the red corpuscles represent nearly one- 

 half of the liquid blood. They contain about 57.7 per cent, of 

 water and 40.5 per cent, of oxy haemoglobin, while the constituents 

 of the stroma inclusive of mineral salts amount only to about 1.9 per 

 cent. Among these constituents Halliburton's cell-globulin is said 



