OF THE ACTIONS OF THE HEART AND ARTERIES. 43 



behind this organ, seems more particularly to preside over its movements, or to rein- 

 force with additional energy whatever it may receive from other sources, especially 

 from the centre of the ganglial system and the other ganglia in the neck and chest. 

 These nerves, according to our own observations, supply the substance of the heart in 

 two ways : 1st, There are numerous branches which proceed from the different plex- 

 uses directly to its muscular texture, and which, dipping between the fibres, give 

 off' minute fibrillae to these fibres next to them in the course of their descent into 

 the substance of the heart. 2d, A large portion also of the nerves of the heart form 

 an t nvelope of the coronary arteries. A part of these seem to follow the arteries 

 throughout their distributions ; but, before the coronary arteries have ramified to a 

 great extent, a part ot the nerves surrounding them is detached to the adjoining parts, 

 so that all the nerves which surround these arteries, like a reticulum or sheath, 

 do not accompany the ramifications of the latter to their ultimate subdivisions and ter- 

 minations in the veins, a portion of them appearing to be detached in numerous and 

 minute fibrillse to the immediately adjoining fibres. Thus it will be perceived that the 

 muscular texture of the heart receives directly and mediately a very considerable por- 

 tion of ganglial nerves ; whilst, it may be presumed, that it also receives an accession in 

 those fibrils which terminate with the nutritious capillaries in this particular structure 



The functions of the heart, it may reasonably be supposed, are chiefly the result of 

 the influence which this disposition of the ganglial system of nerves bestows on its 

 structure. In addition to the support which this inference derives from the conforma- 

 tion of the viscus and its relation with the rest of this particular system of nerves, both 

 n. man and the lower animals, experiments which have been performed by different 

 physiologists, prove its accuracy* ; and prove it the more conclusively, inasmuch as 

 they were performed with a view of establishing a different proposition. 



But, although the heart derives its chief influence from the ganglial system, it is 

 ucted on through the medium of the nerves which communicate between this system 

 and the cerebro-spinal, and which seem to convey an additional influence from the lat- 

 ter, to the ganglia and plexuses which immediately supply the heart. And as this 

 communication is more* intimate in the more perfect animals, and the functions of the 

 cerebro-spinal system are more energetic in them, so it appears to follow that the heart's 

 action is more" readily influenced either by the increase or diminution of these func- 

 tions in them, than in the lowest order of animals. 



Another point to which it is necessary to advert, is the question as to the active dila- 

 tion of the heart a function of this viscus much insisted on by Hamberger, and more 

 recently by Carson and others. We doubt not that it actually exists to some extent, 

 in all animals provided with a perfect heart, but we do not believe that it takes place 

 with great energy. If the dilation, however, of the heart, were a mere result of a re- 

 laxation of its fibres, its cavities could not be so quickly and perfectly filled by the 

 mechanical pressure of the blood directed towards them, as we observe that they are ; 

 and dilation would be only the consequence of this pressure, and be proportionate 

 to it. But this is not the case ; for, as far as we could judge from observing the cir- 

 culation in fishes, the dilation seems to precede the flow of blood, the latter appearing* 

 as a consequence of the former. 



Allowing, therefore, that the dilation of the cavities of the heart takes place to a 

 certain extent an extent which it is difficult fully to determine, but which we consi- 

 der much less than that contended for by Hamberger and Carson, one of the causes ct" 

 the flow of blood in the large veins will be apparent. 



The heart is perfectly insensible in its natural state. This was satisfactorily shown in 

 an operation performed by ML Richerand, in 1813, wherein he divided the ribs and re- 



* Willis divided the eight pair of nerves in the neck with a view of paralysing the 

 action of the heart, but death did not supervene until some hours, and in some casee, 

 not until several days, after the operation. In the experiments of Legallois and Dr. 

 Phillips, destruction of the brain and spinal marrow did not necessarily and immediately 

 put a stop to the action of this viscus : although, as should be expected, it was greatly 

 influenced by the privation of a necessary and an accustomed influence. In experi- 

 ments which were performed on several species of fishes, the actions of the heart con- 

 tinued long after the destruction of the cerebro-spinal masses, and frequently for u 

 short time after it was removed from the body. Lastly, foetuses have been born, in 

 which the action of the heart and circulation were perfect, although tiiey wanted both 

 brain and spinal cord : and many of the lower classes of animals have continued to ! ; ' ,. 

 for a very considerable time after decapitation, 



