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CHAP. IV.- Relation of Blood with the Heart. 



1. THE heart possesses the assimilating and the 

 functional life. In this, as in other instances, the assimilating life 

 maintains itself, and is proper, or belonging to this place or structure : 

 the functional, accomplishes those phenomena which are peculiar to 

 the organ, and superadded to the common properties of life. The 

 objects of a full investigation of the physiology of this organ would 

 be comprised in a history of the chances of its principle and struc- 

 ture, from the state of the maternal ovum till it has attained a fixed 

 and perfect constitution, when its phenomena and relations are to 

 l>e specified, and their dependences inquired into. 



2. The principal questions here to be discussed are, 



1st, Are the assimilating and functional properties of the heart 

 distinct or identical? 



2nd, What are the relations of blood in the cavities of the heart, 

 with respect to the above properties] 



3. 1. The first question is to be determined by facts which 

 prove whether any of the properties concerned in the action, &c.of 

 the heart would cease if the connexion of this with other parts were 

 intercepted. It is difficult to experiment upon this subject with 

 satisfactory results: a short view, however, of the state of the ques- 

 tion may here be admitted. 



4. The nerves of the heart, it is said, may be divided, and the 

 heart will continue to contract and dilate: hence it is inferred, that 

 the action of the heart is independent of the nervous centres; or, in 

 other words, that its properties are all inherent, or maintained in its 

 own structure. But the facts are too imperfect to justify this in- 

 ference, as the heart possesses a power of acting/or a time under a 

 privation of an ascertained cause, and a necessary one to the per- 

 manence of its action, viz. after the circulation of blood has ceased. 



5. On the other side of the question, it is urged, the power of 

 action of the heart is destroyed by an injury, or breaking down of 

 the structure of the medulla spinal is. A dependence is inferred from 

 this fact, but with less propriety than from the last; for it has been 

 shewn that the simplest mode of intercepting a communication, as 

 by division, &c. is in some degrf-e liable to the suspicion that the 

 remote change takes place by an influence, or properties, conferred, 

 foreign ones; and cettainly in no case will the injury of one part 



