Hcem rrhage. 125 



mass of blood exerts a certain amount of pressure and in conse- 

 quence the cells and tissues are forced apart, displaced by the in- 

 vading blood ; and hollow viscera are occluded by the coagulated 

 blood. Even small haemorrhages in the brain, according to their 

 precise location, occasion a loss of function in the area affected, 

 perhaps even to the extent of complete obliteration of conscious- 

 ness ; in the case of spinal haemorrhages palsies ensue : hccmorrhage 

 under the mucous lining of the air passages (fracture of the 

 trachea and larynx) forces the same into the lumen to such a 

 degree that the air passage is constricted and death from asphyxia 

 may result. 



The escaped blood usuall}^ coagulates, precisely as the blood in 

 venesection (cf. chapter on thrombosis). Should this clot remain 

 in the tissue or in one of the serous sacs it acts as an inflammatory 

 excitant ; it attracts the leucocytes by chemotaxis and causes a 

 limiting zone of connective tissue proliferation about it. This 

 gradually forms a capsule about the collection of blood, transform- 

 ing it into a haemorrhagic cyst, often called a haematoma, in which 

 the disintegrating blood exists, partly as soft, elastic, fibrinous 

 masses, of a reddish or brownish color, partly as liquid serum ex- 

 pressed from the clot. Such h.Tmatomata, sometimes approaching 

 the size of a human head, are not infrequently seen in the spleen 

 of domestic animals, around the kidneys in swine, and in the pelvic 

 cavity of cattle as the results of contusion haemorrhages. On the 

 other hand the penetration of leucocytes to the mass and the pro- 

 liferation of fibroplastic and angioplastic tissue leads to the resorp- 

 tion of the blood. Its disintegrating elements are taken up by 

 the amoeboid cells and carried away ; the plasma is absorbed by 

 the cells and may pass off through the lymph paths. The red 

 corpuscles both in the tissue lymph and in the blood vessels begin 

 to swell and lose their color or to become shriveled. The coloring 

 matter, haemoglobin, having been dissolved out may soak through 

 the tissue dift"usely or may become deposited in the form of flakes, 

 granules or more rarely as crystals through the tissue. The 

 crystalline form is especially apt to occur where the blood has been 

 stagnant (haematoma), appearing as ruby-red to brown, minute 

 rhombic plates and needles (iron-free haematoidin) ; the granules 

 are yellow and angular, sometimes give an iron reaction (haemosi- 

 derin), sometimes undergo a change like the crystals b\' which the 

 iron is separated from the haemoglobin, iron-free haematoidin 

 (haemofuscin) remaining. 



