CHAP. IV.] THE BLOOD. METHODS OF RESEARCH. 



205 



doubtedlyan admirable one, and relieves the mind of the experimenter 

 from the fear of an accidental leak an eventuality which, unfortu- 

 nately, does occur where many stop-cocks are freely surrounded by air. 



FIG. 45. ALVEKGNIAT'S MERCURIAL PUMP, FITTED UP AS IN AN ACTUAL EXPERIMENT. 



