THE VASCULAR, RESPIRATORY, AND ALIMENTARY 

 SYSTEMS. DEMONSTRATIONS. 



CHAPTER XXX. 

 CIRCULATION OF THE BLOOD. 



Proofs of the Circulation of the Blood. A mammal is anaesthetised 

 with ether and chloroform. 



The external jugular vein is exposed and the carotid artery. A clip 

 is placed on the jugular vein. Note the central end of the vein 

 empties, while the peripheral end becomes enlarged. A clip is next 

 placed on the carotid artery, the central end becomes distended and 

 pulsates, while the peripheral end shrinks and ceases to pulsate. The 

 clips are now removed and two ligatures placed in position (but 

 not tied) under each vessel. The vein is pricked. Note the dark 

 blood which flows out from the peripheral end steadily and without 

 force. The vein is then tied above and below the opening. The 

 artery is next pricked. Note the blood spurts out forcibly and in 

 jets from the central end. The artery is then tied above and below 

 the opening. 



A tracheal cannula is placed in the trachea and connected with 

 the artificial respiration apparatus. The sternum is divided in the 

 mid-line, and the thorax opened, so as to expose the heart. The 

 pericardum is slit open. Observe the systole and diastole of the 

 auricular appendices and ventricles. Ligatures are now passed under 

 the superior and inferior venae cavae and tightened. The heart quickly 

 empties. On loosening the ligatures observe the immediate filling of the 

 right heart. A ligature is next passed under the aorta and tightened. 

 Observe the engorgement, firstly, of the left, and $hen of the right 

 heart. On loosening the ligature note the effect. A ligature is next 

 passed under the pulmonary artery and tightened. The right 

 heart becomes engorged while the left empties. On loosening the 



