THE HEART. 



165 



carbonate solution, may be introduced into the jugular vein and so slipped 

 down into either the right auricle or the right ventricle, or may be similarly 

 introduced into the carotid artery and with care slipped down through the 

 aorta, past the semilunar valves, into the left ventricle, and having been 

 thus introduced may, like the ordinary canula used in studying arterial 

 pressure ( 104), be brought into connection with a mercury manometer. 

 In this way, as in the case of an artery, a graphic record may be obtained of 

 the changes of pressure taking place in either of the above three cavities. 

 But the changes in the ventricular cavities are so great and rapid, that the 

 inertia of the mercury, an evil in the case of an artery, comes so largely into 

 play that the curve described by the float on the mercury is far from being 

 an accurate record of the changes of pressure in the cavity. 



The mercury manometer may, however, be made to yield valuable results 

 by adopting the ingenious contrivance of converting the ordinary manometer 

 into a maximum or a minimum instrument. 



The principle of the maximum manometer, Fig. 53, consists in the introduction 

 into the tube leading from the heart to the mercury column of a (modified cup- 



[FiG. 53. 



The Maximum Manometer of Goltz and Gaule. At e a connection is made with the tube lead- 

 ing to the heart. When the screw-clamp k is closed, the valve v comes into action, and the in- 

 strument, in the position of the valve shown in the figure, is a maximum manometer. By revers- 

 ing the direction of v it is converted into a minimum manometer. When k is opened, the varia- 

 tions of pressure are conveyed along a, and the instrument then acts like an ordinary manometer. 



and-ball) valve, opening, like the aortic semilunar valves, easily from the heart, 

 but closing firmly when fluid attempts to return to the heart. The highest pres- 

 sure is that which drives the longest column of fluid past the valve, raising the 

 mercury column to a corresponding height. Since this column, once past the 

 valve, cannot return, the mercury remains at the height to which it was raised 

 by it and thus records the maximum pressure. By reversing the direction of the 

 valve, the manometer is converted from a maximum into a minimum instrument. 



The maximum manometer applied to the cavity of either ventricle or of 

 the right auricle, gives a record of the highest pressure reached within that 

 cavity, and the minimum manometer similarly shows the lowest pressure 

 reached, during the time that the instrument is applied. 



The maximum manometer thus employed shows that the maximum pres- 



