x THE FORE-BRAIN 573 



due to stimulation of the cortex are similar to those excited reflexly 

 from the cutaneous or mucous sensory surfaces. 



The effects on the heart of cortical stimulation are very variable, 

 according to Francois - Franck and Pitres ; acceleration and 

 retardation of rhythm appear irregularly in the course of a single 

 experiment, independently of the seat of stimulation. This con- 

 stantly occurs on applying currents capable of provoking epileptic 

 fits in animals that are in light narcosis. During the tonic phase 

 of the epileptic attack there is thus a more or less marked slowing 

 of cardiac rhythm (from 150 to 110 beats per minute), while during 

 the clonic stage the rhythm is accelerated (e.g. rises from 125 to 

 250 beats per minute). In curarised animals too, in which the 



Fio. 293. Voluntary acceleration of cardiac rhythm with no change in the respiration. Observa- 

 tion made on a young man by Patrizi. The arrow indicates the commencement of the 

 voluntary effort to accelerate the beat of the heart. The upper line is the tracing of thoracic 

 respiration by Marey's pneumograph ; the lower, the pulse tracing from the left hand, taken 

 with Luciani's volumetric glove. 



convulsions of the voluntary muscles are eliminated, the same 

 cardiac reactions can be seen on strong cortical excitation. 



Changes of cardiac rhythm can also be observed on moderate 

 cortical excitation of brief duration, which is incapable of producing 

 epileptic seizures. In these cases the effect consists in regular 

 acceleration or retardation of rhythm. The form of the reaction 

 is independent of the site of the stimulation in the motor area, 

 and seems to depend more upon the intensity of the stimulus : 

 inhibition is usually due to sudden, strong excitation, acceleration 

 to mild and prolonged stimuli. 



In respect of these cardiac reactions the excitable surface of 

 the brain may again be compared to a sensitive surface, and there 

 is no reason for assuming that the motor area contains special 

 moderator and accelerator centres for the heart. 



