115 



independent of the excitement to action which they receive 

 through the nervous system. 



The best ground for the hypothesis of Carpenter is that, ac- 

 cording to him, the heart continues to heat, although it is not 

 exposed to any excitation in certain circumstances. He says : 

 "When every source of excitement is excluded, we cannot but 

 perceive that these actions take place with a spontaniety which 

 can scarcely be accounted for in any other way than by con- 

 sidering them as expressions of the vital activity of the compo- 

 nent cells of these forms of muscular tissue, which manifests it- 

 self in this mode, when the developmental life of the cell has at- 

 tained its maturity. And this view is strikingly confirmed by" 

 what we know of the origin and termination of these movements. 

 For the action of the heart commences when, as yet, its contrac- 

 tile parietes consist but of an assemblage of ordinary-looking 

 cells, no proper muscular tissue being evolved, and no nervous 

 system being yet developed, from which the stimulus to the move- 

 ment can proceed ; and it is impossible to assign any other cause 

 for the movement under such circumstances, than the attributes 

 inherent in the tissues which perform it." 



The first thing to be said against the view of Carpenter is, that 

 his hypothesis is not necessary ; because it is possible to assign 

 another cause for the movement of the heart under the circum- 

 stances he speaks of. This will be proved hereafter. 



The doctrine of Carpenter implies, that the degree of irrita- 

 bility (motility, motor force, contractility, never mind the 

 name) is greater in the heart than in the other muscles which 

 have no spontaneous action. This is not the case. The degree 

 of irritability, as judged by its duration after death, is generally 

 greater in the muscle of animal life, than in the heart. The ac- 

 cepted sentence of Haller, Cor ultimum moriens, generally, is 

 not true. 



If Carpenter was right, we should see, during life, the appa- 

 rently spontaneous contractions which take place in all the con- 

 tractile tissues after death ; because their irritability is at a 

 higher degree in the first, than in the second case. Besides, we 

 should not see oxygen, or red blood, diminish the frequency of 

 the beatings of the heart ; and black blood, or carbonic acid, in- 

 crease that frequency. 



