THE BLOOD-PLATELETS 83 



for in the observations we have described there is no fragmenta- 

 tion of either the white or red corpuscles, and we are compelled 

 to consider the platelets as related to some change in the plasma. 

 The single or multiple thromboses which may be met with in 

 pathological conditions may not improbably be due to some 

 toxic material in the blood, which, acting somewhat in the 

 way described in the above experiments, may induce profound 

 changes in the plasma with a resulting accumulation of platelets 

 — an addition to those which may already exist. 



If we assume that blood-platelets pre-existent in blood dis- 

 appear so rapidly that their absence in a blood-film can be 

 explained away by such an hypothesis, certain experiments of 

 Bizzozero which are seldom quoted are opposed to such a view. 

 These observations were made to ascertain if it was possible 

 to entirely remove the blood-platelets from the circulation, and 

 then to see with what rapidity these were regenerated in the 

 blood. In the process of defibrinating blood Bizzozero dis- 

 tinguishes two periods ; during the first " lagen sich an den 

 Schlagstabschen eine dichte Blutplattchenschicht ab"; while 

 during the second, laminae of fibrin are spread upon this aggluti- 

 nated granular mass of platelets. The blood-platelets, therefore, 

 do not rapidly disappear in shed blood, but can be removed 

 from blood before fibrin collects upon them. By bleeding dogs 

 from the carotid to the extent of almost half the total mass of 

 blood, robbing this of platelets and fibrin, returning the strained 

 and warmed fluid to the animal by the external jugular vein, 

 and repeating this procedure about nine times in two hours, 

 Bizzozero effected an almost entire disappearance of the plate- 

 lets. 1 Five days later the normal number of 200,000 per c.mm. 

 was not only restored, but actually exceeded by 165,000. From 

 the fact that the animal, except for a transient haemoglobinuria, 

 remained in health, it is a logical inference that the blood- 

 platelets, unlike the red and white corpuscles, are in no way 

 essential for existence. 



It appears to us that this experiment, which is one of 

 undoubted interest, demonstrates in the first place that the 

 platelets possess considerable resistance to damage ; secondly, 

 that the blood returned to the animal is robbed of much of its 



1 The blood was examined and the platelets counted after dilution with several 

 times its bulk of 14 per cent. MgSOj, or with a mixture of 1 part of 1 per cent, 

 osmic acid and 3 parts of 1 per cent. NaCl. 



