I III \< TION OP Till III \l;r 



i r 



A searching investigation into tin- physical principles involved in ti 

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

 ever, shown tli.it considerable ••inns are incurred, the inertia of the 



moving m;i^ of fluid in the tubing and the □ Bsity of using levers in 



order to secure records being responsible for mosl of them cf. V* 

 gers). Their elimination has recently been achieved by usin<_ r ,-i so-called 

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

 panying figure. It consists of a wide 'jlass tube .1. connected above with 

 a hollow brass cj linder /»'. provided with a stopcock C, the lumen of which 

 tapers from below upward till it assumes tin' same diameter as an ap 

 ture in the segmenl capsule l>, above it thai is. a capsule cu1 away at one 

 end -which is :\ mm. in diameter ami covered with rubber 'lam. By ad- 

 justment of this stopcock the piils.-it ions of the fluid in .1 ami B can be 

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



Fig. .'.! Optical records of intraventricular pressure; a-!, auricular systole; bd. prespuygi 

 period; >'•/. sphygmic period; after f. diastole. Instrument trying dc{ 



were employed in taking the curves. (From Wigl 



segmenl capsule. A small piece of celluloid carrying a tiny mirror r< 



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 lighl placed at some distance from it is focused on the 

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

 mirror ami again reflected from the larger mirror is adjusted s, 



impinge upon a moving photographic plane travelling at a uniform ratl- 

 in a suitably constructed photographic apparatus. By the us< I such 



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

 struments are eliminated, because there is no moving m;is> of fluid and 

 there are no levers to set up spurious vibrations. Curves -••cured by 



the use of this instrument are shown in I 



Two objects must he kept in view in analyzing the curves 1 Cui 



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

 termine the exact moment during the cardiac cycle at which BUCh p 



