Section of Medical Science. 509 



nesses in the interior of arteries, or irregularities, over which the 

 blood, in passing, produces the sound ; but it is not heard in the 

 healthy heart, the internal surface of which is exceedingly irregular; 

 nor is it necessarily present in aneurisms, rough and irregular on 

 their inner surface, from shape, or from deposition of fibrine ; the 

 sound, on the contrary, being frequently heard when there is no de- 

 viation from the natural state of the interior surfaces of the heart 

 or arteries. 



The second part of the paper developed Dr. Corrigan's views. 

 His theory is, that the sound depends on the simultaneous presence 

 of these two conditions, viz. 1st, a current-like motion of the blood 

 (instead of its natural equable movement), tending to produce cor- 

 responding vibrations on the sides of the cavities or arteries through 

 which it is moving ; and, 2ndly, a state of the arteries or cavities 

 themselves by which, instead of being kept in a state of tense ap- 

 proximation on their contained inelastic blood (which would neces- 

 sarily prevent any vibration of their sides), they become free to vi- 

 brate to the play of the currents within on their parietes ; and by 

 those vibrations cause, on the sense of touch, " fremissement" and 

 on the sense of hearing, " bruit de soufflet." It was shown that these 

 two conditions are present in the parietes of the ventricle, and the 

 currents of blood striking against them in cases of narrowed auri- 

 culo-ventricular openings ; in the enlarged and tortuous arteries of 

 the placental portion of the uterus permitted by their very free ana- 

 stomosis with veins and sinuses, and other causes, to become par- 

 tially flaccid in the intervals of the heart's contractions, and the ir- 

 regular currents necessarily assumed by the blood in rushing along 

 these comparatively flaccid tubes at their next diastole ; and that si- 

 milar conditions exist in the analogous state of the vessels in aneu- 

 rismal dilatations of tortuous arteries. The presence of the two 

 conditions was also applied to explain the mechanism of the sound 

 in permanent patency of the mouth of the aorta, in the large arteries 

 of animals dying of haemorrhage, and in various other instances. In 

 conclusion, two experiments were detailed, in which, in one instance, 

 a small bladder, and in the other a portion of the gut of an animal, 

 was interposed between two cocks, the upper or nearer being the 

 cock of a water-cistern, and the lower or further constituting the 

 discharging orifice of the bladder or gut, and water then allowed to 

 flow through from the cistern. The sound " bruit de soufflet" and 

 the sensation "fremissement" were perceptible in the intervening 

 bladder or gut, until (from the upper pipe pouring in fluid faster 

 than the lower discharged it) the bladder or gut became tense, and 

 then both sensations ceased, the passage of the fluid through, ne- 

 vertheless, continuing all the time. The experiment with the blad- 

 der was applied to explain the occasional presence and absence of 

 " bruit de soufflet" in aneurisms, the sound being present in an aneu- 

 rism when, from any circumstance connected with it, its parietes can 

 become at all flaccid in the intervals of the heart's contractions, — 

 not being heard if the parietes remain tensely applied to their con- 

 tained fluid. 



