92 EXPERIMENTAL PHYSIOLOGY 



blood are drawn up into the glass tubes. The first appearance 

 of a clot is determined by drawing out a small glass rod. Each 

 tube must have its own rod. From time to time (every 20 to 

 30 sees.) the rod is to be inserted and the first clot sought. 



After having become practised in the method blood is drawn 

 from the human ear or finger and the clotting time determined. 

 In the case of the finger, it should be exercised for several 

 seconds, then a handkerchief wrapped tightly around it at the 

 second joint, the first joint being bent at a right angle. The 

 skin is punctured now a little below the base of the nail. 



In every subject three determinations, which check within 

 the limits of experimental error, should be made. Obtain 

 observations from as many different subjects as possible. 



D. Place a drop of human blood or rabbit's blood on a 

 slide and cover with a cover-slip. Observe the blood with a 

 microscope from time to time so that the fine structure and 

 behaviour of a clot may be seen. Between observations cover 

 the slide with a moist chamber cover containing wet filter paper 

 plastered to the inside; otherwise the blood will dry before it 

 clots. 



Summarize the information which you have obtained form 

 the above experiments. 



