Scientific Proceedings. 



(217) 47 



details of processes commonly seen clinically but about which 

 much theorizing must be done in the wards. 



25 (117). "On the blood-pressure relations in mitral insuffi- 

 ciency and stenosis": W. G. MACCALLUM and R. D. 

 MCCLURE. 



In the course of experiments like those described in the pre- 

 ceding communication, blood pressure in various portions of the 

 circulatory apparatus was recorded after mitral insufficiency had 

 been produced by introducing a curved knife hook into the left 

 auricular appendage and cutting some portion of the mitral valve 

 — a systolic murmur could then be heard especially loud over the 

 auricle and along the pulmonary veins with usually a thrill felt 

 over the auricle. Interest attaches especially to the exact explan- 

 ation of the hypertrophy of the right ventricle since, as Gerhart 

 points out, there is an obvious obstruction to the flow of blood 

 through the mitral orifice into the ventricle. 



This is true only when the left ventricle at once accomodates 

 itself to the condition by dilating to receive the excessive amount 

 of blood which accumulates in the auricle, that is, the amount 

 thrown into it from the right ventricle plus the amount regurgitated, 

 and then succeeds in expelling it all. Unless this happens the 

 auricle is unable to empty itself and a condition arises in which the 

 amount of blood circulated is smaller than normal, the remainder 

 being stagnant in the pulmonary circulation and the right ventricle 

 is found to be driving a uniformly smaller amount of blood into a 

 cavity (the pulmonary circulation) in which there is some stagnant 

 blood and into which more is forced from the left ventricle during 

 systole. The elevation of pressure from this stagnation need not 

 be great and in the experiment where these conditions seem to 

 prevail the pressure in the pulmonary is not much elevated. 

 Ordinarily, however, the left ventricle dilates to receive the exces- 

 sive blood, then regurgitates some and discharges nearly the 

 normal amount into the aorta. The right ventricle then attempts 

 to discharge into the pulmonary circulation the same large amount 

 at the moment when the stronger left ventricle is also forcing into 

 that cavity the amount constantly regurgitated. The pulmonary 

 pressure is again not much elevated — not more than before but 



