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EXPERIMENTAL PHYSIOLOGY 



carotids having been first ligatured and the vertebrals occluded by 

 a wire passed immediately in front of the axis vertebra, drawn tightly 

 and securely fastened behind. Another ligature is made to include all 

 the remaining structures of the neck except the trachea. The head is 

 cut off by an incision in front of these ligatures passing between the 

 occiput and atlas. Oozing of blood is stopped by application of dilute 

 suprarenal extract, and the skin is fastened over the cut end of the 

 neck. Before tying the arteries, a tube has been inserted into the 

 trachea, and artificial respiration is kept up by pumping air into the 



FIG. 66. Diagram of Marey's cardiograph, a, Receiving tambour for fixing over 

 apex beat ; b, recording tambour connected with a by rubber tvibing, with 

 a lateral opening closed by a clip. 



lungs and allowing it to escape by a side tube. This air is warmed, 

 and the body is further kept warm after decapitation by placing it on 

 a warmed plate and covering it with cotton-wool. In such a prepara- 

 tion the circulation is maintained (although the pressure is somewhat 

 low) and the tissues continue to live for several hours. Spinal reflexes 

 can be studied in it (see Chapter XXV.). The heart is exposed by 

 severing four or five ribs or rib-cartilages on each side by bone forceps, 

 and with the same instrument cutting through the sternum near its 

 lower end, and raising the detached part forcibly, along with the cut 

 ends of the ribs. This bony and muscular flap may, if necessary, be 

 removed altogether after tying a string or wire tightly round its. 



