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2. On the Circulation of the Blood, and the Difference of the 

 Laws of Fluids moving in living and dead tubes. Part I. 

 By Sir Charles Bell. 



The author commenced with a eulogy of Mr Hunter, and of 

 his experiments upon the arteries ; and proceeded to illustrate 

 the elasticity and muscularity of an artery. 



The author's experiments were made on the human frame, by 

 takinjf advantage of the amputated limb on the instant of its 

 separation from the body. He made a section of the artery so as 

 to present a piece in the form of a ring, — he slit this ring, and it 

 sprang open to a certain extent. Putting it in water, it was 

 found in the morning reversed or bent the other way. On taking 

 a larger portion of the artery, which was straight, and slitting it 

 up, it immediately bent backwards in a semicircular form. 



The author gave this explanation of these facts : — On the cir- 

 cular portion of the artery being cut up, the elastic power pre- 

 vailed to a certain degree ; but continuing to be opposed by the 

 circular muscular fibres until the vital power was exhausted, then 

 the elasticity so entirely prevailed as to bend the ring in the re- 

 verse position. 



But on slitting up the long straight piece of the artery, it im- 

 mediately curled back, for there are no longitudinal muscular 

 fibres to prevent the elasticity having instant effect. 



The author then went into a description of the different mode 

 and time of action of the muscular fibre, shewing that we must 

 not retain the idea first presented to us in the voluntary muscles, 

 but contemplate the same property of action in the muscular fibre, 

 where it enters into the composition of particular organs, and 

 when it is made subservient to the function, acting in a different 

 time and mode, and being sometimes not excitable by acrid or 

 mechanical stimulus : hence inferring, that we must not expect 

 to excite the muscular coat of an artery by irritating it as we 

 might do a voluntary muscle. 



The author took a portion of an artery of a square form, and 

 found that, by appending weights, it was equally elastic in all 

 directions; on which he argued, — Since the artery is full of blood 

 when it receives the systole of the heart, on the acknowledged 

 laws of hydraulics, that an impulse upon fluids is propagated 

 equally in all directions, it must follow that the artery dilates in 

 the transverse as well as the longitudinal direction. 



