2O6 



THE HEART. 



or from which it had been removed, ceased to beat; and finally that the anterior 

 end of the median nerve (from the first three segments) did not control the heart 

 beat of its territory, since, in its absence, the first three segments would continue 

 to beat provided there was a nerve-fiber bridge to the posterior part of the median 

 ganglion. 



FIG. 1 1 8. Diagram of the heart, pericardium, and principal blood-vessels of Limulus. 

 veins in half tone. Seen from the haemal surface. 



Arterial trunks in black; 



The following is a record of some experiments made three years later, by 

 R. Pearl, a student in Dartmouth College working under my direction: 



A. July 27, 1900. The heart was exposed and cleaned of connective tissue. 



a. Stimulation of the median longitudinal nerve with a weak current 

 caused one long continuous systole, b. Stimulation of the lateral cardiac nerves 

 caused an increase in the strength of the systole and in the rapidity of the beat. 

 The rhythmical beat continued during the stimulation. On removing the elec- 

 trodes a complete diastole followed. During the stimulation there was no com- 

 plete relaxation of the heart muscles between systoles, c. Stimulation of the 



