COAGULATIOX OF HIJX)!) 317 



of minor importance to the pathologist) or Uberate it only after their disinte- 

 gration. As far as pathological processes go, the latter seems to be the case, the 

 disintegration ajjparently occurring whenever tiie leucocytes come in contact with 

 a foreign body or with dead and injured tissues. The stroma of red corpuscles 

 also contains thrombokinase."" Of the substances that may be isolated from 

 tissues, ce-phalin is found especially active in producing thrombosis, and may be 

 related to or identical with the thromboplastin.^" 



Tissue Coagulins. — Among the other i)oints that are of importance in i)atho- 

 logical conditions is the fact that not only the leucocytes, but also tissue-cells, 

 can liberate fibrin-forming substances {coaffidtiifi is the non-committal term ap- 

 plied by Loeb). Howell considers that the effect of the tissue "'coagulins" is 

 merely to neutralize the antithrombin of the blood, if such coagulins actually 

 e.Kist; possibly there is thromboplastin in the tissues. These coagulating agents 

 are present in tissue extracts and are liberated whenever the tissues are injured; 

 muscle is rich in coagulin, as are also the liver and kidney, and, which is par- 

 ticularly important, the blood-vessel wall (L. Loeb). Pieces of these tissues 

 })laced in contact with fibrinogen solution will bring about prompt clotting. An- 

 other important fact is that the coagulins, whether derived from leucocytes or 

 from the tissues, have a certain degree of sjiecificity — that is, they act solely or 

 most rapidly with fibrinogen of blood of the species from which they are obtained.'" 

 In some instances this specificity is absolute, but more generally (particularly in 

 the mammalia) it is only relative. Loeb also found that the amount of tissue 

 coagulin was not decreased in organs altered by phosphorus poisoning, although 

 during experimental autolysis the coagulins disappear. Wlien tissue coagulins 

 and blood coagulins act together, the effect is greater than the sum of their inde- 

 pendent actions, indicating the probability that they combine in some way to 

 produce a particularly active coagulin. The blood coagulins are quite different 

 from the tissue coagulins in many important respects, and the coagulins cannot 

 be looked upon as a single substance of different origins. 



Blood-platelets. — It is still undetermined just what part the platelets play in 

 coagulation. The well-known observation that in thrombosis the fibrin is often 

 first formed about masses of platelets clinging to the wall of the vessel indicates 

 that they participate in the process, and Bizzozero and others have maintained 

 that the platelets and not the leucocytes are the source of the prothrombin. 

 Numerous studies on the relation of the platelets to disease conditions have in- 

 dicated a certain parallelism between their number and the tendency to coagula- 

 tion observed in the various diseases (Welch). Howell believes the platelets to be 

 the chief source of thromboplastin, which neutralizes the antithrombin of the 

 blood and thus causes clotting. Wright and Minof^ find that a viscous meta- 

 morphosis of the platelets is intimately associated with the early stages of coagu- 

 lation. Bordet and Delange consider the platelets of more importance than the 

 leucocytes in producing participants of the coagulating mechanism. The histo- 

 logical evidence of the importance of the platelets in thrombus formation is con- 

 clusive (see Zurhelle, Derewenko), and Cramer and Pringle"^ state that coagulation 

 cannot occur without platelets. However, the blood of fishes, birds and reptiles 

 clots although no platelets are found in these animals. Human thoracic lymph 

 also is devoid of platelets yet it clots; but it may contain products of platelet 

 disintegration to explain this clotting (Jordan)."'* Kemp'* concludes, from a 

 thorough review of the subject, that the blood-platelets are usually normal or 

 subnormal in number during acute infectious diseases, but increase rapidly if the 

 disease terminates by crisis; iii pernicious anemia the number is always greatly 

 diminished, although in secondary anemias they may sometimes be increased; in 

 purpura hemorrhagica the number of plates is enormously diminished, which is 



«« Barratt, Jour. Path, and Bact., 1913 (17), 303. 



"Howell, Amer. Jour. Physiol., 1912 (31), 1; MacLean, ibid., 1916 (41), 250; 

 1917 (43), 586. 



'"Leo Loeb, Univ. of Penn. Med. Bull., 1904 (16), 382; Muraschew, Deut. 

 Arch. klin. Med., 1904 (SO), 187. 



" Jour. Exp. Med., 1917 (26), 395. 



" Quart. Jour. Exper. Physiol, 1913 (6), 1. 



" Anat. Rec, 1918 (15), 37. 



"" Jour. AmQv. Med. Assoc, 1906 (46), 1022. 



