ON THE MOTION OF THE BLOOD. 83 



neuro-electric state of the vessels, and which contains all the heads 

 of the detail. Mr. Charles Bell has lately published this hypothesis 

 as his own,* but most of the facts adduced by him to prove that 

 the resistance to the blood's progress is removed by a repul- 

 sion between it and the vessels may be explained by the suction 

 influence of the heart which he altogether overlooks. 



(G) These oscillations are quite imaginary and now disallowed. 

 Although variations of dilatation must affect the course of the 

 blood through vessels, it is difficult to conceive how any regular 

 action of them can assist it. 



(H) In a young lady whom I lately attended for chronic ca- 

 tarrh accompanied by violent cough, from which she ultimately 

 recovered, all the veins of the back of the hands and fore-arms 

 distinctly pulsated synchronously with the arteries. 



The heart of mammalia and birds has no peculiarity necessary 

 to be mentioned here. In most amphibious animals, the arteries 

 spring from the right ventricle, with which the left, that sends off 

 no vessel, communicates i hence their circulation continues under 

 water. The heart of Jish is extremely small, and has but one au- 

 ricle and ventricle, the latter propelling the blood to the gills, from 

 which it streams through a large artery. Neither blood vessels 

 nor absorbents liave been discovered in insects ; yet a large tube, 

 close at each end, pulsates in their back. With respect to the 

 mollusca : The cuttle fish has three detached hearts, consisting of a 

 ventricle only, two for the gills and one for the aorta ; the re9t have 

 a single heart, the blood of the cava passing through the gills 

 before it reaches the heart. The same is the case with the Crus- 

 tacea, and their heart has no auricle. Worms have circulating 

 vessels distinctly contracting and dilating, but no heart. Zoo- 

 phytes have no heart, nor circulating system, properly so called. 

 In the echinus indeed there are two vessels that run along the 

 intestines and are thought to be an aorta and vena cava. 



* An Essay on the Forres which circulate the blood, being an examination 

 of the difference of the motions of fluids in living and dead vessels. 181!). 



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