434 BLOOD AND LYMPH. 



of other substances. Calcium solutions added in quantity sufficient 

 to notably raise the calcium percentage of the plasma distinctly 

 favor the process of clotting and may lead to the formation of 

 intra vascular clots. So, too, injections of thrombin or of leucocytes 

 as obtained from macerated lymph glands cause clotting. In 

 this latter case, however, it has been noticed that if the quantity 

 injected is not sufficient the coagulability of the blood may be 

 distinctly retarded instead of being accelerated. This fact has been 

 accounted for on the hypothesis that in the disintegration of the 

 foreign leucocytes two products are formed, one tending to acceler- 

 ate coagulation (positive phase of the injection) and one tending to 

 retard it (negative phase). Lilienfeld* has made this hypothesis 

 more specific by showing that lymphocytes (and blood plates) 

 yield a nucleoprotein which in turn on decomposition furnishes a 

 second nucleoprotein, leuconuclein, whose presence favors coagula- 

 tion, and a simple protein, histon, whose action retards clotting. 

 Delezenne f has still further added to the hypothesis by experiments 

 which indicate that the element favoring coagulation (leuconuclein) 

 is removed or destroyed by the liver. When an insufficient quan- 

 tity of leucocytes is injected into the circulation the histon action 

 may predominate, and thus retard coagulation, while with larger 

 quantities and a more extensive decomposition the leuconuclein 

 may bring about clotting before it is completely destroyed by the 

 liver. 



Means of Hastening or of Retarding Coagulation. Blood 

 coagulates normally within a few minutes, but the process may be 

 hastened by increasing the extent of foreign surface with which it 

 comes in contact. Thus, agitating the liquid when in quantity, or 

 the application of a sponge or a handkerchief to a wound, hastens 

 the onset of clotting. This is easily understood when it is remem- 

 bered that the breaking down of leucocytes and blood-plates is 

 hastened by contact with foreign surfaces. It has been proposed 

 also to hasten clotting in case of hemorrhage by the use of ferment 

 solutions or of tissue-extracts containing some thrombokinase. 

 Hot sponges or cloths applied to a wound hasten clotting, probably 

 by accelerating the formation of ferment and the chemical changes 

 of clotting. Coagulation may be retarded or be prevented alto- 

 gether by a variety of means, of which the following are the most 

 important : 



1. By Cooling. This method succeeds well only in blood that 

 clots slowly for example, the blood of the horse, bird, or terrapin. 

 Blood from these animals received into narrow vessels surrounded 

 by crushed ice may be kept fluid for an indefinite time. The blood 

 corpuscles soon sink, so that by this means one may readily obtain 

 * Lilienfeld, " Zeitschrift f. physiol. Chemie," 18, 473. }Loc. cit. 



