CHAP, iv.] THE VASCULAR MECHANISM. 241 



ampulla then cause movements of the corresponding lever. When the 

 pressure, for instance, on the ampulla in the auricle is increased, the 

 auricular lever is raised and describes on the recording surface an 



FIG. 37. MAREY'S TAMBOUR, WITH CARDIAC SOUND. 



A. A simple cardiac sound such as may be used for exploration of the left 

 ventricle. The portion a of the ampulla at the end is of thin indiarubber, stretched 

 over an open framework with metallic supports above and below. The long tube b 

 serves to introduce it into the cavity which it is desired to explore. 



B. The Tambour. The metal chamber m is covered in an air-tight manner 

 with the indiarubber c, bearing a thin metal plate m' to which is attached the lever I 

 moving on the hinge h. The whole tambour can be placed by means of the clamp 

 cl at any height on the upright s'. The indiarubber tube t serves to connect the 

 interior of the tambour either with the cavity of the ampulla of A or with any other 

 cavity. Supposing that the tube t were connected with 6, any pressure exerted on a 

 would cause the roof of the tambour to rise and the point of the lever would be pro- 

 portionately raised. 



ascending curve ; when the pressure is taken off the curve descends ; 

 and so also with the ventricle. 



The 'sound' may in a similar manner be readily introduced through 

 the carotid artery into the left ventricle and the changes taking place 

 in that chamber also explored. 



When this instrument is applied to the right auricle and 

 ventricle some such record is obtained as that shewn in Fig. 38 

 where the upper curve is a tracing taken from the right auricle, 

 and the lower curve from the right ventricle of the horse, 

 both curves being taken simultaneously on the same recording 

 surface. 



In these curves the rise of the lever indicates pressure exerted 



F. 16 



