VASO MOTOR NERVES. 91 



COAGULATION OF BLOOD. 



Experiment 37. A. Expose the carotid artery and jugular vein 

 in an anesthetized rabbot. Treat each as follows : Tie a ligature 

 around the vessel as close to the heart as possible. When rilled 

 with blood tie a second ligature 2 cm. above the first, and a 

 third 2 cm. above the second. Crush the vessel between the 

 first and second ligature by means of a hemostat without 

 rupturing the wall. Later, when the rest of the experiment is 

 completed look for an intravascular clot in each vessel " pocket." 

 Explain. 



B. Insert a cannula into the carotid artery of the other side, 

 Draw 5 c.c. of blood into each of the test tubes prepared as 

 follows, after which, the time required for the first appearance 

 of a clot is determined. 



1. Clean keep at room temperature. 



2. Clean keep at 37 C. to 40 C. 



3. Clean-keep at C. to 5 C. 



4. Containing sand with which the blood is to be shaken. 



5. Thoroughly coated inside with a vaseline or paraffin oil. 



6. Containing a small amount of potassium oxalate with 



which the blood is to be shaken. After ascertaining 

 that oxalated blood does not clot add a drop or two 

 of 5% CaCl 2 solution, increasing the quantity if 

 necessary. 



7. Vaselined centrifuge the blood, separating the plasma 



and keeping it for observation. 



C. Several glass tubes from 3 to 4 cm. long (3 to 4mm. dia.) 

 and tapere'd nearly to capillary dimensions at one end are 

 oiled inside. A short length of rubber tubing is doubled at 

 one end and tied with thread. This tube should fit easily but 

 snugly to the glass tubes and is used as a pipette bulb to suck 

 blood into the glass tubes. 



A rabbit's ear, with hair closely clipped and washed thor- 

 oughly long enough before to permit drying, is oiled. When 

 the observer is ready to note the time, a vein is punctured by 

 holding the under surface of the ear against a cork and plunging 

 a sharp three-cornered needle through it. Four samples of 



