260 THE BLOOD AND THE LYMPH 



The above analysis of the blood of a man shows the relative general 

 amounts of the blood's components. In woman the salts and the water 

 are in somewhat larger proportion. Under the head of proteids were 

 included serum-albumin, paraglobulin, nucleo-proteid, jecorin, and 

 thrombin, while the " extractives" were such various substances as 

 dextrose, glycogen, fats, lecithin, lutein, lactic acid, kreatin, kreatinin, 

 urea, uric acid, xanthin, and cholesterin. The salts may be noted from 

 the preliminary complete list of the blood's constituents on page 255. 

 They are chiefly chlorides, phosphates, carbonates, and sulphates of 

 the common tissue-metals. 



COAGULATION of the blood is a function essential to the continuance 

 of life, for without it any wound, however small, in the tissues would 

 cause death by hemorrhage. This fact is all too often illustrated in 

 the victims of hemophilia, commonly called "bleeders." Something 

 is lacking congenitally in their blood so that it does not coagulate. In 

 consequence of this defect they almost always die before maturity by 

 hemorrhage from an open tooth-socket, the nose, or from some minor 

 wound of the skin. 



Given a multitude of soft corpuscles floating in a thin liquid: the 

 evolutionary problem was to contrive a way of uniting them quickly 

 into a solid mass dense enough to obstruct the blood-stream flowing 

 swiftly and under considerable pressure through an injured vessel. For 

 this purpose nothing could be better than a mesh of fine but tough and 

 elastic fibers quickly formed in the blood when suddenly needed but by 

 no means until then nor in any other place than at the seat of injury. 

 Such indeed is the fibrin which forms in extravasated blood or in the blood- 

 vessels whose walls have been badly injured, and thus made dangerous 

 to the organism. How is this fibrin net-work formed and from which 

 of the blood's components ? It is not quite certain as yet. 



As the name of the thrombocytes (given by Dekhuysen to the platelets) 

 implies, it is perhaps this third sort of blood-particles which have most 

 to do with coagulation. In 1904 Biirker studied them in great detail. 

 He found that when a drop of blood was placed on a polished bit of clean 

 paraffin in a moist-chamber, in half-an-hour or less the thrombocytes 

 rose to the top of the drop, being lighter than the plasma, and with no. 

 dependence on the leukocytes. Under these excellent microscopic 

 conditions the coagulation of the drop of blood could be accurately 

 studied. It was seen that the coagulation- time depended directly on 

 the relative number of thrombocytes present in the drop, and that those 

 substances which inhibit coagulation (for example leech-extract) do 

 so by preventing the decomposition of the thrombocytes. On the 

 other hand, those agencies which hastened coagulation killed the platelets. 

 Just before clotting was apparent in the blood (of man, cats, dogs, 

 hens, frogs, etc., at least), the thrombocytes were observed by Ducceschi 

 to agglutinate in white masses a quarter or a half of a millimeter in 

 diameter on the sides of the containing vessel, and this occurred from 

 forty to one-hundred-and-twenty seconds before any fibrin had formed. 



