THE ACTION OF THE HEART 



147 



was placed in one of the ventricles, another in the auricle or aorta, the 

 tube being inserted in the former case through one of the large veins at 

 the root of the neck ; in the latter case through the carotid artery. The 

 intracardiac pressure curves obtained in this way marked a great ad- 

 vance over the methods that had previously been used to study the events 

 of the cardiac cycle, but they were so faulty in comparison with tracings 

 taken by more modern methods that it is not worth while considering 

 them any further here. 



The physical errors involved in the use of the older instruments were due mainly to 

 the elastic recoil of the membranes, etc., used in their construction. A great improve- 

 ment in technique was afforded by the use of the spring manometer of Hiirthle (see page 

 128), which was connected with one of the heart cavities by a cannula filled before 



Fig. 32. Diagram of Wiggers' optical manometer. The wide glass tube (A) (connected 

 with the ventricle, etc.) is connected with a brass cylinder (B) provided with a stopcock (C), 

 the lumen of which comes in apposition with a plate (a) having a small opening in it. The 

 freedom of communication between B and a is regulated by the position of the tap. Above a is 

 a segment capsule (&) 3 mm. in diameter and covered by rubber darn. This carries a small 

 mirror (C) fastened so that it pivots on the chord side of the capsule. Above the capsule is 

 arranged an inclined mirror, from which a strong beam of light is reflected on to the mirror 

 (c) on the capsule. This beam then travels back and the mirror () is adjusted so that it 

 impinges on a moving photographic plate. The slightest movements of the small mirror (C) 

 are thus greatly magnified. 



insertion with some anticoagulant fluid. The cavity of the tambour was made as 

 small as possible, and either left empty or filled with the anticoagulating fluid. 



A searching investigation into the physical principles involved in taking records of 

 sudden changes in pressure by such instruments has, however, shown that considerable 

 errors are incurred, the inertia of the moving mass of fiuid in the tubing and the 

 necessity of using levers in order to secure records being responsible for most of them 

 (cf. Wiggers). Their elimination has recently been achieved by using a so-called 

 optical manometer, one of which (Wiggers') is shown in the accompanying figure. It 

 consists of a wide glass tube A, connected above with a hollow brass cylinder B, pro- 

 vided with a stopcock C, the lumen of which tapers from below upward till it assumes 

 the same diameter as an aperture in the segment capsule fc, above it that is, a capsule 



