THE MICROSCOPE IN PATHOLOGY. 



271 



substance (globulin, fibrino-plastic substance), which en- 

 ters into union with a similar (fibrinogenous) substance, 

 so as to form fibrin, the molecules of which have a great 

 attraction for each other, producing a characteristic mi- 

 croscopic network of round filaments. 



Thrombi must not be confounded with the coagula 

 found in the dead. If the death-struggle has been long 

 coagula are generally found in the right side of the heart, 

 often extending into the pulmonary artery. A thrombus 

 is lighter, firmer, and drier than a coagulum, and is often 

 made up of concentric layers. 



Cross-section through a thrombus by ligation of the crural artery, thirty-seven days 

 old ; hardened in alcohol, treated with dilute acetic acid, and then with a little ammonia- 

 a. Capillaries, b. The cell-net of the colorless blood-corpuscles. In the basis-substance 

 the contours of the red blood-corpuscles. After RINDFLEISCH. 



A thrombus once formed either organizes or softens. 



If it organizes, the thrombus is gradually changed into 

 connective tissue. This is by virtue of the vital power 

 of the bioplasts, or white corpuscles. Thrombi have been 

 produced in animals by ligation, and cinnabar injections 

 into the blood have shown the w r andering leucocytes, 

 carrying cinnabar, at work in the blood-clot. They send 

 out processes in various directions, which touch each 

 other and form a more delicate net with nuclei at the 

 points of intersection (Fig. 220). 



