118 



depend on the nervous system, appear to me to be greatly mis- 

 taken. They make a confusion between two things, greatly dis- 

 tinct, one from the other : they conclude from the fact that the 

 nervous system is able to act on the heart, that its influence is 

 necessary. It is the same kind of mistake which is so frequently 

 made as to the influence of the nervous system on nutrition, on 

 secretions, and on animal heat ; because that system is able to 

 act upon these functions, it is concluded that its influence is ne- 

 cessary. 



The first argument to be adduced against the writers who ad- 

 mit, as necessary, the influence of the nervous system on the 

 heart, is, that they change only the ground of the difficulty in 

 doing so. Instead of having to explain why the heart acts rhyth- 

 mically, they have to explain why the nervous system acts rhyth- 

 mically on the heart. Not only they have not explained this 

 rhythmic action of the nervous system, but, as far as I know, 

 they appear not to have been aware that this was to be explained. 



The second reason I will mention, is the fact, so well esta- 

 blised by my friend Professor Lebert, that, in embryos, the heart 

 beats when it is merely composed of cells, and when the nervous 

 system has not yet appeared 



A third reason is, that, either in monsters, or in animals ope- 

 rated on by physiologists, there has been a long persistence of the 

 beatings of the heart when a part of the cerebro-spinal centre did 

 not exist, or had been removed. Any part may be in that case, 

 even the medulla oblongata, as I have discovered. (See Art. xvi. 

 p. 40.) 



In opposition to the idea that the beatings of the heart depend 

 on the microscopical ganglia existing in that organ, I will say, 

 that, besides the fact that the heart beats in embryos before the 

 nervous system exists, and besides the improbability that such a 

 small amount of nervous matter should have so great a power, 

 there are two good reasons against this strange theory : 

 1. There have been found no ganglia, large or microscopical, in 

 the auricles, in the sinuses of the pulmonary veins, or in those 

 veins. All these parts, nevertheless, may continue to beat a long 

 while, (even for hours,) after they have been separated from the 

 ventricles where are the microscopic ganglia. 2. Rhythmical 

 movements may exist in a'great many other muscular parts of the 



