146 



THE CIRCULATION OF THE BLOOD 



Intracardiac Pressure Curves 



The earliest method for taking such curves consisted in introducing 

 into the cardiac chambers and the blood vessels of the horse, so-called 

 cardiac sounds. These consisted of a more or less rigid tube furnished at 

 one end with a little elastic bag or ampulla and connected at the other 

 with a tambour, by means of rubber tubing. One of these little bags 

 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 



C-- 



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 (fc) 3 mm. in diameter and covered by rubber dam. 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. 



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 improvement in technic was afforded by the use 

 of the spring manometer of Hiirthle (see page 126), which was connected 

 with one of the heart cavities by a cannula filled before 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. 



