THE COAGULATION OF THE BLOOD 209 



other formed elements of the blood, makes it necessary to examine 

 the evidence pertaining to their origin somewhat more closely. It 

 is believed (a) that they are not present in the normal circulating blood, 

 and appear only if the latter is brought in contact with a foreign body, 

 and (6) that they are preexisting and constant constituents of the 

 blood. The former view contends that the thrombocytes do not be- 

 long to the class of the formed elements, but appear together with 

 those chemicophysical alterations which indicate the beginning of the 

 coagulation of the blood. They constitute, so to speak, condensation 

 or precipitation products of the globulin constituents of the blood. 

 This view 1 has found support in the following observations. It is 

 true that the platelets are absent from the blood of several animals, 

 for example, from that of the frog, fishes and birds. It is also conceded 

 that they are not very conspicuous in the blood of several mammals, 

 but may be rendered more prominent in these animals by first injuring 

 the wall of one of their blood-vessels or by introducing a foreign body 

 into their circulatory system. Under these conditions they may be 

 seen to collect upon the injured area in the form of a deposit. More- 

 over, Buckmaster has shown that blood drawn into the sterile serum 

 of another animal, does not always display these bodies, but exhibits 

 them very promptly if it is collected in the loop of a platinum wire. 

 Furthermore, while they are not present in fresh plasma which has 

 been rendered non-coagulable by sodium oxalate or peptone, they ap- 

 pear in this plasma in large numbers after it has been cooled for a 

 period of about 24 hours. Lastly, blood which has been treated with 

 an anticoagulating agent while still in the circulatory system, does 

 not show them, nor do they appear in it later on after its withdrawal 

 from the body. 



The evidence which may be submitted in favor of the second view, 

 advocating the preexistence and independency of the thrombocytes, 

 is as follows: Quite aside from the fact that we are in possession of 

 definite methods for their isolation, we possess in the mesentery of the 

 guinea-pig and in the wings of the bat preparations in which it is possi- 

 ble to observe them directly. Moreover, they are present in large 

 numbers in the blood-vessels of the subcutaneous connective tissue of 

 various animals and particularly in that of the new-born rat. If to 

 these facts are added the observations regarding their ameboid 

 motion, 2 as well as certain observations pertaining to their physical 

 and chemical characteristics, such as their stickiness, their great vul- 

 nerability and their very manifest power to incite the coagulation of 

 the blood, 3 it cannot be doubted that they are preformed and function- 

 ally distinct constituents of the blood. 



1 Wooldridge, Die Gerinnung des Blutes, Veit and Co., Leipzig, 1894, and 

 Loswit, Virchow's Archiv fur path. Anat., cxvii, 1889. 



2 Deetjen: Virchow's Archiv fur path. Anat., cxlvi, 1901, and Deckhuysen, 

 Anatom. Anzeiger, xix, 1901. 



3 Eberth and Schimmelbusch, Die Thrombose, Stuttgart, 1888, and Klopsch, 

 Anat. Anzeiger, xix, 1901. 



14 



