XI.] GENERAL PROPERTIES OF NERVOUS TISSUE. 121 



be seen in the thin membranous pericardium 

 beating with considerable regularity and force. 

 Pinching up the pericardium with a fine pair of 

 forceps, cut it away from the surface of the heart 

 then tilt up the apex of the ventricle ; a small 

 band of connective tissue will be observed passing 

 from the posterior surface of the ventricle to the 

 adjoining wall of the pericardium. Seizing this 

 band with the forceps, divide it between the 

 forceps and the pericardial wall. Lift up the 

 apex of the ventricle, by means of this band, 

 and with a sharp pair of scissors cut through the 

 aorta?, the superior venae cavse, the inferior vena 

 cava, and the surrounding tissue. Take care not 

 to injure the sinus venosus. Place the heart in 

 a watch-glass, moistening it when necessary 

 with normal saline solution. The beats will 

 either not be interrupted at all or for a very 

 short time. 



In cold weather the heart may stop on being 

 removed from the body, but if the heart be 

 warmed by putting the watch-glass containing 

 it in the palm of the hand, the beats will be 

 resumed. 



2. Lifting up the apex of the ventricle by means of 

 the same band as before, cut through the ventricle 

 with a sharp pair of scissors at its upper third 

 The lower two-thirds of the ventricle will remain 

 motionless without any spontaneous beat; the 

 upper third and the auricles will continue to 

 beat with regularity. 



