PI.ATK LXXXYI. 



Fir. 209.-End view of the block by which the sphygmograph rests on the bones of the wrist sh 

 <erew, B, by which the pressure exercised by the spring on the artery can be varied ( 39). 



Fin. 9p9&. BregoeV* Improvement ( 39). 

 FlU 210. ilode of measuring pressure ( 39). 



FIG. 2iT. Schema for demonstrating the nature of the arterial movements. A. Glass tube which represents 

 the heart. B. The tube by which A communicate* with a cistern at a height of ten or twelve feet above it. (A 

 much smaller head of water is sufficient.) C. The lever by which the two valves K and 1) are worked, the 

 same act which shuts the one opening the other. F. Commencement of the experimental tul>e, which is of 

 black vulcanite. At F the tube communicates with a long vertical tube of glass, only part of which is seen ; 

 It is closed at the top, and usually shut off from F by a pinchcock. At O the tube pasoes under the spring of 

 the Bphygmogvaph, the frame of which rests on a block (below o). By error, the tulxj has lieen drawn on the 

 wrong side of the block. H. The blackened plate of the sphygmograph. To the left of it is seen the cylin- 

 der, with its needle for recording the time which intervenes between the opening and closing of the aortic 

 valve, D. L. A rod which is firmly fixed iii the lever, and is connected by two cords, one of which is elastic 

 with the cylinder ($ 40). 



