182 



Dr. J. 0. W. Barratt. The Nature of the 



mentioned coagulation was delayed, the onset occurring at room temperature 

 in 25 to 60 minutes, the normal period being about 15 minutes. 



The effect of peptone upon the coagulability of the blood was further 

 studied in rabbits in a series of experiments in which blood was withdrawn 

 by means of a paraffined cannula from the internal carotid artery, about 

 5 minutes after intravenous injection of peptone, and received into : (1) a 

 paraffined tube ; (2) a second paraffined tube ; and (3) a glass tube not 

 paraffined. Immediately before injection blood was collected from the 

 internal carotid artery into (4) a glass tube not paraffined. Tube 1 was 

 centrifugalised and liquid plasma (1«) obtained, free from blood cells, which 

 was preserved in a paraffined tube. In this way it was found possible to 

 compare the time of onset of coagulation under different experimental 

 conditions. Thus in one experiment, which may be taken as a type, a firm 

 clot formed in (4) at the end of 10 minutes ; a soft clot formed in (3) at the 

 end of 25 minutes (remaining still soft at the end of 3^ hours) ; the blood in 

 (2) formed a soft clot at the end of two hours, still remaining soft and not 

 retracted at the end of two days ; the plasma in (la) remained perfectly liquid 

 at room temperature (15° to 17° C.) for four days, changed to a somewhat 

 thick liquid at the end of five days and had formed a soft clot at the end of 

 seven days. Experiments of this kind cannot be satisfactorily carried out if 

 instead of peptone red cell stromata are employed, owing to the exceedingly 

 lethal character of such injections. A similar defect of coagulability may 

 be observed when peptone acts upon a solution of fibrinogen in vitro • thus 

 in the series of tests given on p. 186 a fairly firm clot formed in the second 

 tube, while in the next three tubes the clot became increasingly soft, being 

 exceedingly so in the fifth tube ; nevertheless at the end of two days all 

 these tubes contained clots of normal firmness.* 



It is clear from the above that the effect of intravenous injection ' of 

 thrombokinase is essentially different from that of injection of thrombin. 

 In the latter case an abundant intravascular formation of fibrin takes place 

 attended with reduction of the amount of fibrinogen contained in the 

 circulating fluid, while after the injection of thrombokinase in amounts 

 equivalent, as far as coagulant action upon fibrinogen in vitro is concerned, 



* The effect of injection of peptone into a dog, under conditions similar to those 

 obtaining in Experiment 3, differs somewhat from that observed when a rabbit is 

 employed. If the dog employed for experiment is resistant, the same delay of coagulation 

 is observed, but the clot formed is much softer and retraction of the clot is imperfect or 

 absent. If, however, a dog which is susceptible to the action of peptone is ke2i>t fasting 

 for 48 hours before injection of peptone, then blood collected from the internal carotid 

 artery remains, as is well known, for a long time liquid, though containing fibrinogen in 

 apparently undiminished amount and clotting on the addition of thrombin. 



