Coagulant of the Venom of Echis carina tus. 179 



of fibrin in the blood-vessels, particularly of the lungs. This method has 

 been adopted in the present investigation. 



The injection of a solution of thrombin was carried out after the manner of 

 the following experiment : — 



Experiment 1. — A solution of fibrinogen measuring 16 c.c. was prepared, as 

 described in the next section, from 16 c.c. of rabbit's blood plasma. To this 

 1*2 c.c. of a suspension of the red-cell stromata of the rabbit* was added, 

 together with 1*2 c.c. of 0'6-per-cent. calcium chloride solution. A firm clot 

 was formed at the end of 30 minutes at 37° C. After the lapse of a further 

 period of 60 minutes 17 c.c. of fluid was expressed from the clot by means of 

 a glass rod ; this was injected into the vein of the ear of a rabbit weighing 

 850 grm. At the end of injection, which occupied nine minutes, the animal 

 became convulsed and died four minutes after the completion of injection. 

 A post-mortem, examination was made without delay : the blood in the heart 

 and great blood-vessels was fluid ; the coagulation time of blood taken from 

 the heart was two minutes ; 4 c.c. of blood obtained on opening the heart 

 coagulated slowly at room temperature, forming a moderately firm clot, which 

 had retracted to about the normal extent next morning ; the lungs collapsed 

 rapidly upon opening the chest. 



When sections of the lung are made after intravenous injection of thrombin, 

 fibrin masses are found in the blood-vessels in amount depending upon the 

 quantity of thrombin injected, but in no case are fibrin masses observed in 

 more than a small number of the blood vessels. The appearance of the fibrin, 

 which is illustrated elsewhere.t varies considerably, being obviously in part 

 determined by the time elapsing between injection and death. Sometimes, 

 though rarely, a very fine network is seen, resembling that observed when 

 a section is made of a clot formed in a solution of fibrinogen after the 

 addition of thrombin, or of thrombokinase and calcium chloride, as in the 

 experiments recorded in the next section. More usually an irregular coarse 

 network is seen, resulting from the contraction or compression in the 

 blood stream of the delicate fibrils first formed, the process being com- 

 parable to that occurring when blood is whipped. Frequently the change 

 is carried a step further and dense masses of fibrin of varying size are 

 seen, sometimes forming irregular plugs partly filling the arterioles, some- 

 times in the form of threads of varying length in the capillaries. It is 

 found that after the injection of large quantities of thrombin the amount 

 of fibrin obtainable when blood collected from the heart is allowed to 



* Cp. Experiment 2, p. 180. 



t J. 0. Wakelin Barratt, loc. cit. 



