THE MAIN FACTS OF THE CIRCULATION. 139 



FIG. 37. 





Apparatus for Investigating Blood-pressure, At the upper right-hand corner is seen, on an 

 enlarged scale, the carotid artery, clamped by the forceps bd, with the vagus nerve v lying by its 

 side. The artery has been ligatured at I' and the glass canula c has been introduced into the 

 artery between the ligature I' and the forceps bd, and secured in position by the ligature I. The 

 shrunken artery on the distal side of the canula is seen at ca'. 



p.b is a box containing a bottle holding a saturated solution of sodium carbonate or a solution 

 of sodium bicarbonate of sp. gr. 1083, and capable of being raised or lowered at pleasure. The 

 solution flows by the tube p.t regulated by the clamp c" into the tube t. A syringe, with a stop- 

 cock, may be substituted for the bottle, and attached at c". This, indeed, is in many respects a 



