Animal Morphology. 97 



Concerning their distribution to the capillary termini of 

 arteries, nothing is known with certainty ; but with regard 

 to the heart, the distribution of its ganglia and nerves 

 indicates an arrangement of a most comprehensive cha- 

 racter for complete diffusion throughout that organ. For 

 our more precise knowledge about th'e nerves of the heart, 

 we are chiefly indebted to Dr. R. Lee and Dr. James 

 Pettigrew. 



It will be perceived that the endocardium, which is con- 

 tinuous with the arteries and veins, has no relation in its 

 muscular membrane to the heart, but the muscular coat of 

 the heart is the excessive development of a distinct tripartite 

 membrane namely, the Ganglionic muscular membrane ; 

 and this membrane is, as it were, wedged in between the 

 junction of the spent and depurated blood and the new 

 blood by the lymphatic system, and the fresh blood from 

 the lungs made ready to go its round of vital operations 

 between waste material and fresh matter to the several 

 tissues of the body. 



If it be true that ganglia are distributed to the arterial 

 muscular fibres at their distal termini and at the heart, and 

 that this membrane is really an economiser and distributor 

 of electricity, then its freedom of action and independent 

 origin as a distinct tripartite membrane can be easily ex- 

 plained. 



For, in such case, the heart will be ruled in the degree of 

 its action in sympathy with the body generally not from 

 the kind of blood flowing through it, unless when the kind 

 also extends to the quantity ; but it will be more influenced 

 by the effect which blood has in relation to chemico-vital, 

 and therefore electric changes which are going on in remote 

 parts of the body, and thus tone down or rouse the heart 

 up to more energy, according as these changes modify the 

 electric equilibrium in morbid function and nutrition; and 



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