THROMBOSIS 271 



formed of red corpuscles, these thrombi do not stain at all like 

 normal corpuscles, presumably because a certain proportion of 

 the hemoglobin has been altered or lost through hemolysis. Of 

 particular interest is their reaction to Weigert's fibrin stain, by 

 which they often, but not always, stain intensely ; a fact that 

 has been the cause of much confusion in earlier studies. Flex- 

 ner 1 first appreciated the nature of these thrombi as origi- 

 nating from agglutinated red corpuscles, although Klebs, Zieg- 

 ler, and others had earlier suggested that hyalin thrombi were 

 formed from red corpuscles. Boxmeyer 2 independently arrived 

 at the same conclusion as Flexner, in studying hyalin thrombi 

 as the cause of necrosis in the liver of animals infected with the 

 hog-cholera bacillus. Flexner produced hyalin thrombi by 

 injecting corpuscles agglutinated by ricin, or by injecting ricin 

 itself, or hemolytic substances such as ether or foreign serum. 

 As the thrombi become old, the corpuscles lose their form and 

 color and produce the typical hyalin appearance. Pearce 3 

 proved conclusively the dependence of the thrombus formation 

 upon agglutination, for he secured the same results, including 

 the liver necrosis, by injecting specific agglutinating serums. 

 He states that fibrin threads may occasionally be found at the 

 periphery of the larger thrombi, but never in the smaller ones. 

 The tendency of the thrombi to stain like fibrin by Weigert's 

 method is observed particularly when the tissues have been 

 hardened in Zenker's solution. It is extremely probable, from 

 Flexner's observations, that in the thrombosis produced by 

 injecting various toxic substances into the blood, the so-called 

 "fibrin-ferment thrombosis" the thrombi are merely agglutina- 

 tive thrombi, devoid of fibrin ; this is undoubtedly true for 

 many of the thrombi observed after poisoning with the pow- 

 erfully agglutinative snake venoms (see Chap. viii). On 

 the other hand, some, at least, of the hyalin capillary thrombi 

 are undoubtedly composed of soft masses of fibrin which have 

 not become fibrillar, although the successful staining by fibrin 

 stain is not final proof of the fibrinous nature of a thrombus. 



Secondary Changes in Thrombi. The changes that 

 occur in thrombi after they have existed for some time are largely 

 due either to ingrowth of new tissue or to calcification, the latter 

 of which will be considered in a separate chapter. The 

 only other change of interest from the chemical standpoint 

 is the central softening which may occur in any large thrombus, 



1 Jour. Med. Research, 1902 (8), 316. 



2 Jour. Med. Research, 1903 (9), 146. 



3 Jour. Med. Research, 1904 (12), 329; ibid., 1906 (14), 541. 



