HEMORRHAGE 243 



Arnold l found that when capillaries from which diapedesis had 

 occurred were stained by silver nitrate, dark areas were found 

 between the endothelial cells. As silver nitrate is a stain for 

 chlorides, and darkens intercellular substance because it is rich 

 in sodium chloride (Macallum), it is probable that there is an 

 increase in the amount or a difference in the method of combina- 

 tion of the chlorides of the cement substance between the endo- 

 thelial cells, at the places where red corpuscles escape. 



Hemorrhage in cachectic conditions is often ascribed to 

 changes in the vessel- walls due to malnutrition, but it is diffi- 

 cult to imagine capillary walls suffering from lack of nourish- 

 ment, even with the poorest of blood, and it seems more probable 

 that the hemorrhages are due, even in cachexia, to chemical 

 constituents of the blood that injure the endothelium. 



Changes in the Extravasated Blood. These begin 

 soon after its escape. In most situations sufficient fibrin fer- 

 ment is formed to lead to prompt clotting, but in the pleura 

 and other serous cavities the blood may remain fluid for some 

 time, probably because of lack of cellular injury that might 

 cause liberation of fibrin ferment. If the blood does not be- 

 come infected, the rapidity of subsequent changes depends chiefly 

 upon the location and amount of blood. Small extravasations 

 of blood into the tissues are subjected to the action of the tissue 

 cells and of leucocytes emigrating freely from the capillaries ; 

 large masses of blood are but little affected by these agencies, 

 the leucocytes within the mass soon die, and secondary changes 

 go on very slowly. In small subcutaneous hemorrhages (e. g., 

 a bruise) enzymes from the invading leucocytes and tissue-cells 

 soon dissolve the small quantities of fibrin present ; even earlier 

 the stroma of the red corpuscles is so altered that hemolysis 

 occurs and the hemoglobin escapes and diffuses into the tissues. 

 This hemolysis may be brought about by the action of proteo- 

 lytic enzymes on the corpuscles, or by the hemolytic action of the 

 products ofproteid splitting, Soon the hemoglobin disinte- 

 grates, forming the masses of pigment so characteristic of old 

 hemorrhagic areas, and also giving rise to the discoloration ob- 

 served beneath the skin in the later stages of resorption of 

 hemorrhagic extravasations. The first products of the splitting 

 of hemoglobin are: (1) The proteid, globin, which constitutes 

 94 per cent, of the hemoglobin; and (2) the iron-containing 

 coloring-matter, hematin (in the absence of oxygen the pigment 

 is reduced hematin or hemochromogeri). As hematin may be 

 experimentally obtained by the action of proteases upon hemo- 

 1 Virchow's Arch., 1875 (62), 157. 



