CHANGES IN THE CIRCULATION OF THE BLOOD. 



75 



as the new tissue is formed. This is called " organization of the thrombus, " 

 but in reality the new connective tissue is produced, not from the cells 

 of the thrombus itself, but from the cells of 

 the walls of the affected trunk, from whose 

 vessels the new blood-vessels of the thrombus 

 also arise (compare page 104). In this way 

 the vessel may be completely and perma- 

 nently occluded, or, more rarely, one of several 

 channels may be established through the new 

 connective-tissue mass (Fig. 11). 



Thrombi in veins may lead to hyperaemia 

 and cedema ; in arteries, to an anaemia whose 

 significance will vary greatly, depending upon 

 the situation of the occluded vessel. l 



Agglutinative Thrombi.* The recent studies 

 on agglutination and haemolysis (see p. 190) 

 have led to the belief that certain thrombi oc- 

 curring in infectious diseases as well as under 

 other conditions may arise from the develop- 

 ment of agglutinative substances in the blood. 

 Under the action of these substances the red 

 blood cells may, without the formation of 

 fibrin, clump together, leading to thrombosis. 

 Such thrombi are called agglutinative thrombi. 

 Such thrombi have been repeatedly observed 

 in typhoid fever and other infectious. In such masses of agglutinated 



red blood cells the individual corpuscles 

 may not be seen, the whole presenting 

 a hyaline mass. Thus may be formed a 

 variety of the so-called hyaline thrombi. 

 Welch 3 has suggested the probability 

 that under similar conditions leucocytes 

 also may form agglutinative thrombi. 



Hyaline Thrombi. Under a variety 

 of conditions, but especially in local and 

 THE BLOOD VES- general infections and in intoxications, 

 there is present in the capillaries and in 

 the small arteries and veins a homogene- 

 ous, translucent, nearly colorless material, partially or wholly blocking 

 the vessels. This hyaline material, whose origin is still in doubt, has in 

 some instances a staining reaction similar to fibrin. In other cases hyaline 

 thrombi are probably special forms of agglutinative thrombi (see above). 



1 For a thorough and admirable consideration of the subject of thrombosis and em- 

 bolism with bibliography, consult Welch, Albutt's "System of Medicine," vol. vi., pp. 

 155 et seq. 



- Consult Flexner " On Thrombi Composed of Agglutinated Red Blood Corpuscles," 

 Journal of Medical Research, vol. viii. , p. 316. 



3 Welch, Huxley Lecture, Medical News, October 18th, 1902, p. 731. 



FIG. 12. AN EMBOLUS LODGED 

 AT THE POINT OF DIVISION OF AN 

 ARTERY. 



This is a portion of clot which has 

 been detached from a point above 

 and swept along the blood current. 

 It has increased in length by coagu- 

 lation at its free extremities. 



FIG. 13. FAT EMBOL 



SELS OF THE LUNG 

 This followed bone fracture. 



