36 



Dr. J. A. Mc William. On the 



[Dec. 18, 



prevent the inhibitory result. Curiously enough, stimulation of the 

 visceral peritoneum has an entirely different and indeed an entirely 

 negative result ; it is followed by no perceptible change in the heart's 

 action. Even strong interrupted currents, and strong mechanical, 

 chemical, and thermal stimuli applied to the visceral peritoneum, seem 

 to be quite without effect on the cardiac beat. Powerful electrical 

 stimulation of the whole thickness of the walls of the stomach and 

 intestine has no perceptible effect on the heart. Pinching, crushing, 

 and tearing of these parts are equally ineffective ; and so are chemical 

 and thermal irritants. 



Here I must advert to an experiment described by Marshall Hall in 

 " Todd's Cyclopaedia of Anatomy and Physiology " (article Heart). 

 He states that when the stomach of an eel was crushed by a violent 

 blow with a hammer, the heart stood still for a considerable length 

 of time, and this even though the animal's brain and spinal cord had been 

 previously destroyed. From this he argues that the cardiac action can 

 be inhibited by impulses originating in the stomach, and acting upon 

 the heart without the mediation of the cerebro- spinal system at all. 



Now I have many times violently crushed the stomach of an eel by 

 means of large and strong pliers, and I have never observed any 

 cardiac arrest resulting therefrom. This statement holds both in the 

 case of eels that have had their brain and spinal cord intact, and 

 in eels that have had these organs destroyed. It would seem therefore 

 that the cardiac inhibition observed by Marshall Hall was in all pro- 

 bability not simply due to the crushing of the stomach — to which he 

 ascribes it. It must have occurred as a consequence of some effect of 

 the blow other than the crushing of the stomach. Indeed, his method 

 of experiment was such as to render possible the agency of many 

 causes other than those strictly dependent on the injury of the 

 stomach ; his method rendered possible the excitation of many nerve 

 impulses besides those generated by the stomach injury. For a severe 

 blow delivered with a hammer upon the intact stomach of an eel would 

 necessarily injure various other structures, and would at the same 

 time give rise to a considerable amount of jar. Injury of such struc- 

 tures adjacent to the stomach as might be effected by a hammer blow, 

 cannot be put down as the efficient cause of the reflex cardiac arrest, 

 since powerful stimulation of these parts (applied so as to obviate the 

 accompaniment of jar) gives rise to no effect at all on the heart's 

 action, provided the brain and spinal cord have been previously 

 destroyed. After destruction of these organs I have, however, in 

 several instances observed a well-marked inhibition of the heart's 

 action as a result of sudden jarring of the animal generally — such 

 jarring as may be caused by forcibly striking the board on which the 

 eel rests. This result does not occur in all cases, but in some 

 instances I have seen it in unmistakable form. Such a jarring was 



