116 



An experiment, consisting in the research of the influence of 

 vacuo on the heart, has been made by Tiedemann and by Dr. 

 S. W. Mitchell, and Dr. T. H. Bache, (see Dunglison's Physiol., 

 vol. ii. p. 150.) It seems to me that the result of this experi- 

 ment is in complete opposition to the doctrine of Carpenter. 

 These experimenters have found that the beatings of a heart were 

 speedily brought to a stand by the exhaustion of the air, and 

 that they were renewed when it was re-admitted. If the view 

 of the eminent British physiologist was right, we ought to see 

 the heart continue to beat in vacuo about the same length of time 

 as it would in hydrogen or nitrogen, because its irritability 

 cannot be suddenly diminished enough by the exhaustion of the 

 air. In these gases the heart of a mammal may beat for five or 

 ten minutes or more, and the right auricle may beat for hours ; 

 and the heart of a frog may beat for one day. It is much more 

 to account for the stopping of the heart's action in admitting that 

 the excitant of that action is removed during the exhaustion of 

 the air. John Reid had found that the heart of a frog had con- 

 tinued to beat in vacua, but how long he does not say.* 



I will relate hereafter many experiments of mine which are in 

 opposition to the theory of Carpenter. 



It is one of the most important questions in physiology, whether 

 the nervous centres, the nerves, and the contractile tissues are 

 able to act without stimulation. This question has not been 

 yet entirely treated by any physiologist. I propose publishing 

 a special paper on the subject. I will merely say here that there 

 may be apparently spontaneous actions in the spinal cord, as well 

 as in the muscles. For instance, very frequently, in a frog, after 

 the removal of the brain and the medulla oblongata, we may see 

 strong movements apparently spontaneous, but when we know 

 that the slightest excitation of the skin, or of any other very sen- 



* Art. Heart, in Todd's Cyclop., vol. ii. p. 611. J. Reid says in the same 

 page, "We ought to be more cautious in admitting the existence of this in- 

 nate moving power, since it is in opposition to a well known law in the 

 animal economy, that though the various tissues of an organised body are 

 endowed with certain vital properties, yet the application of certain exter- 

 nal and internal stimuli is necessary to produce their manifestations of 

 activity. In fact it is from the action and reaction of these tissues and 

 excitants upon each other that the phenomena of life result." 



