THE ACTION OF THE HEART 147 



A searching investigation into the physical principles involved in tak- 

 ing records of sudden changes in pressure by such instruments has, how- 

 ever, shown that considerable errors are incurred, the inertia of the 

 moving mass of fluid in the tubing and the necessity of using levers in 

 order to secure records being responsible for most of them (cf. Wig- 

 gers). Their elimination has recently been achieved by using a so-called 

 optical manometer, one of which (Wiggers') is shown in the accom- 

 panying figure. It consists of a wide glass tube A, connected above with 

 a hollow brass cylinder B, provided with a stopcock C, the lumen of which 

 tapers from below upward till it assumes the same diameter as an aper- 

 ture in the segment capsule 6, above it that is, a capsule cut away at one 

 end which is 3 mm. in diameter and covered with rubber dam. By ad- 

 justment of this stopcock the pulsations of the fluid in A and B can be 

 damped to a greater or less extent before they are transmitted into the 



Fig. 33. Optical records of intraventricuiar pressure; a-l, auricular systole; b-d, presphygmic 

 period; d-f, sphygmic period; after /, diastole. Instruments of varying degrees of sensitiveness 

 were employed in taking the curves. ('From Wiggers.) 



segment capsule. A small piece of celluloid carrying a tiny mirror rests 

 on the rubber dam, being pivoted on the chord side of the capsule. A 

 mirror is attached to the capsule with its plane so adjusted that the 

 image of a strong light placed at some distance from it is focused on the 

 little mirror carried by the celluloid. The ray reflected from the little 

 mirror and again reflected from the larger mirror is adjusted so as to 

 impinge upon a moving photographic plane travelling at a uniform rate 

 in a suitably constructed photographic apparatus. By the use of such 

 an apparatus the chief errors encountered by the use of the older in- 

 struments are eliminated, because there is no moving mass of fluid and 

 there are no levers to set up spurious vibrations. Curves secured by 

 the use of this instrument are shown in Fig. 33. 



Two objects must be kept in view in analyzing the curves: (1) Curves 

 obtained from the different cavities may be compared in order to de- 

 termine the exact moment during the cardiac cycle at which such pres- 



