CONNECTED WITH THE BEAT OE THE MAMMALIAN HEART. 
187 
Unfavourable combinations ai'e ;— 
Rectum and left hand. 
Rectum and right foot. 
Rectum and left foot. 
Thus we see that whereas in combination with a lead-ofF from the mouth the only 
unfavourable extremity is the right arm, this is the only favourable one in combination 
with a lead-off from the rectum ; likewise, any one of the three other extremities 
constitutes a favourable combination with a lead-off from the mouth, and an unfavour¬ 
able combination with a lead-off from the rectum. The reason is obvious : the mouth 
is a point h, the rectum is a point a; the mouth and rectum series of combinations 
with other points a or h are consequently the counterparts of each other. 
The logical completeness of these experimental facts is further borne out by :— 
1. Observations on Quadrupeds. 
2. Observations upon two cases of situs viscerum inversus. 
1. Ohservations on Quadrupeds. —The asymmetry in the distribution of potential 
in the Human body originating from the heart is not found in Quadrupeds so far as 
I have examined them. On Cats, for instance {post mortem, but of course only 
during the continuance of cardiac contractions), the following combinations were found 
to be favourable ;— 
Mouth and either posterior extremity ; 
Eye and either posterior extremity ; 
Rectum and either anterior extremity ; 
Rectum and eye or mouth; 
Either anterior extremity and either posterior extremity; 
whereas the following were found to be unfavourable combinations :— 
Mouth or eye and either anterior extremity ; 
Rectum and either posterior extremity; 
The two anterior extremities ; 
The two posterior extremities. 
These results show that the distribution of potential from the heart occupying an 
approximately median position behind the sternum is in accordance with fig. 7. 
2. Having ascertained the mode of distribution of potential on the normal Human 
body with the heart tilted to the left, I at once sought for a case of situs viscerum 
inversus with the heart tilted to the right. By the kindness of Dr. Cheadle and of 
Dr. Lewis I obtained the opportunity of examining two such cases (one male and one 
female), and found the differences from the normal exactly as expected, viz., the 
favourable combinations:— 
Mouth and right hand ; 
Left hand and left foot; 
Left hand and right foot; 
2 B 2 
