196 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



(d) After the injection draw off successive samples, and note the great 

 prolongation of the coagulation time which is soon produced. 



(e) Dilute some of the blood which does not clot with twice its volume of 

 salt solution, and pass a stream of carbonic acid through the mixture ; co- 

 agulation soon occurs. 



(/) The same experiment may be repeated with the same result, if 

 ' peptone ' plasma obtained by centrifugalising is used instead of the whole 

 blood. 



(g) Finally bleed the animal to death, collecting the blood in three 

 successive glass cylinders. Place them in the ice chest, and examine them 

 a few days or a week later. 



The first lot of blood collected will show sedimentation of corpuscles, 

 and a slight clot at the junction of the corpuscles and supernatant plasma 

 that is, at the place where the white corpuscles and platelets lie. 



The last lot of blood collected shows less sedimentation, and will 

 probably have clotted throughout. This is because the blood removed last 

 has been diluted by tissue lymph, which has passed into the blood -stream in 

 an attempt to increase the volume of the blood, which has been lessened 

 by the previous bleeding ; the clot produced is probably due to the action 

 of thrombokinase. 



The middle sample will show something intermediate between the two 

 extremes, the usual state of things being clot through the sediment, and the 

 plasma above it still fluid.. 



4. Intravascular Coagulation. A solution of nucleo-protein from the 

 thymus, testis, lymphatic glands, or kidney has been prepared beforehand by 

 the demonstrator. It may be prepared in one or two ways. 



(a) Wooldridge's Method. The gland is cut up small and extracted with 

 water for twenty-four hours. "Weak acetic acid (0*5 c.c. of the acetic acid of 

 the ' Pharmacopoeia ' diluted with twice its volume of water for every 100 c.c. 

 of extract) is then added to the decanted liquid. After some hours the pre- 

 cipitated nucleo-protein (called tissue-fibrinogen by Wooldridge) falls to the 

 bottom of the vessel. This is collected and dissolved in 1 -per- cent, sodium 

 carbonate solution. 



(6) The Sodium Chloride Method. The finely divided gland is ground 

 up in a mortar with about an equal volume of sodium chloride. The re- 

 sulting viscous mass is poured into excess of distilled water. The iiucleo- 

 protein rises to the surface of the water, where it may be collected and 

 dissolved as before. 



A rabbit is aneesthetised, and a cannula inserted into the external jugular 

 vein. The solution is injected into the circulation through this. The animal 

 soon dies from cessation of respiration ; the eyeballs protrude and the pupils 

 are widely dilated. On opening the animal the heart will be found still 

 beating, and its cavities (especially on the right side) distended with clotted 

 blood. The vessels, especially the veins, also are full of clot. The blood of 

 the portal vein is usually clotted most. If a dog is employed instead of a rabbit 

 in this experiment, coagulation is usually confined to the portal area. This 

 is related to the greater venosity of the blood in this situation. If venosity 

 is increased in any other area, as by tetanisiiig the muscles of one leg, clot- 

 ting will be found also in the veins of this region. 



