140 FOURTH REPORT — 1834. 



then in parts less and less remote ; but that the power of ch'- 

 culation in each part does not depend upon that portion of the 

 cord from which it derives its nerves. He has proved, by de- 

 cided experiments, that Flourens' opinion of the dependence of 

 the power of the heart upon that part of the central nervous 

 masses which supplies the nerves to the respiratory muscles is 

 unfounded, if that could be doubtful after Cliffs experiments on 

 the Carp, published in the Phil. Trcms. 1815. Dr. Marshall Hall 

 could not observe that opium or spirit of wine, applied to the 

 brain or cord, accelerated the circulation, as recorded by Dr. 

 Wilson Philip. 



From these several experiments we conclude : that the heart's 

 power is inherent, and not derived from the brain or cord ; that 

 it is under the influence of every part of the brain and cord ; 

 that it endures for a time, even when the heart is separated from 

 the body. 



The rhythmical contraction of the heart is an instance of that 

 periodicity which occurs in all involuntary motions, even in the 

 minute oscillations of the fibre on which the contractions of 

 those muscles depend which we call voluntary. The whole con- 

 traction in the one case is periodical, for the stimulus is constantly 

 recurring ; in the other the stimulus is dependent on the will. 

 Though the successive presence of the blood in the different ca- 

 vities of the heart may, as Haller explained, be the ordinary sti- 

 mulus to its activity, yet it cannot be the only one, for the rhyth- 

 mical contraction occurs when the heart is empty, and even when 

 placed in vacuo. Why then does the heart continue to act under 

 such circumstances, and what is the stimvilus ? We have seen, 

 from consideration of the growth of the embryo, that organic 

 activity depends upon the mode in which matter is compounded 

 imder the assimilative process. Those organs which receive 

 more blood, are more active than those which receive less ; and 

 such as are liable to be called into siulden and excessive action, 

 as the voluntary muscles, receive most blood of all : the blood 

 is there for assimilation as it is wanted ; aerated blood, proper 

 temperature, and most probably nervous influence being neces- 

 sary conditions of the process by which each creature is enabled 

 to maintain that form and mixture of its parts which is neces- 

 sary to their life. Nutrition, then, or a constant interchange 

 between the particles of the organ and of the blood, being neces- 

 sarj-, it follows that something has occurred in the organ during 

 its active state, some alteration, which requires repair. Activity 

 has caused a change in that composition of its molecules which 

 nutrition must restore. If the restoration do not occur, the sub- 

 sequent reaction is different, or is impossible. The heart, when 



