THE NEGATIVE PRESSURE IN THE HEART. 25 



position of the animal, will all markedly influence the filling pressure 

 of the auricle, and no doubt the maximal auricular pressure depends 

 far more on the filling pressure than on the force of the auricular 

 contraction. 



The negative pressure in the heart. — The diastole of the ventricles 

 is apparently performed with considerable energy. It has been main- 

 tained, therefore, that the diastole, as well as the systole, results from 

 muscular action. It has been impossible, experimenting upon the frog, 

 to prove the existence of any diastolic force in the excised heart, 

 although Luciani has attempted to do so. 1 



Eoy and Tunnicliffe found that the intracardiac pressure in the 

 frog must be "5 to 1 cm. H 2 above the extracardiac for diastole to take 

 place. 2 Tunnicliffe placed the frog-heart in a chamber, in which the 

 extracardiac pressure could be varied. By means of a byway cannula 

 the heart was fed with a nutrient fluid, at a pressure which also could 

 be varied." The diastole did not take place unless the pressure in the 

 feeding tube was made positive. 



The same conclusion was arrived at by Newell Martin and Donald- 

 son, 4 with regard to the excised mammalian heart. After placing an 

 inflow tube in the vena cava superior, and an outflow tube in one sub- 

 clavian artery, Martin ligatured the branches of the arch of the aorta, 

 the thoracic aorta, and the veme cava?. All connections of the heart 

 with the general circulation were thus removed. The pulmonary 

 circulation and the coronary circulation still continued, for artificial 

 respiration was maintained in the lungs, while a circulation of 

 defibrinated blood was established through the heart at a constant 

 temperature. Under such conditions the heart continued to beat 

 normally for many hours. These authors concluded that if the aspira- 

 tion of the thorax be removed, the right auricle will not receive blood, 

 unless it be supplied to it under a decided, if small, positive pressure. 



On passing a cannula connected with a manometer into one or other 

 ventricle of the dog, Goltz and Gaule obtained evidence of a considerable 

 negative pressure, which appeared in the ventricular cavities at some 

 period of the cardiac cycle. 5 In one experiment with the thorax open, 

 these authors obtained a minimal pressure of - 23 - 5 mm. Hg in the left 

 ventricle. In another experiment with the thorax closed, -52 mm. 

 Hg was recorded. The negativity was only marked when the systole 

 was strong, and the heart emptied well. No evidence could be obtained 

 of a negative pressure during the beat of an excised and empty heart. 

 These results were confirmed by de Jager, 6 who obtained, with the 

 thorax open, the following minimal pressures : — 



- 5 to - 38 mm. Hg. in the right ventricle. 



- 2 „ — 6 „ „ in the right auricle. 



Eolleston 7 obtained a minimal negative pressure in the left ventricle 



'Luciani, "Dell' attivita della diastole cardiaca," Bologna, 1871, 1874, and 1876; 

 Mosso and Pagliani, " Critica sperimentale della attivita diastoliea cardiaca," etc., Torino, 

 1876. 



2 Journ. Physiol., Cambridge and London, 1878-79, vol. i. p. 465. 



3 Ibid., 1896, vol. xx. p. 50. 



4 Mem. Biol. Lab. Johns Hopkins Univ., Baltimore, 1887, vol. iv. p. 37. 



5 Arch./, d. ges. Physiol., Bonn, 1878, Bd. xvii. S. 108. 



6 Ibid., 1883, Bd. xxx. S. 506. 



7 Journ. Physiol., Cambridge and London, 1887, vol. viii. p. 250. 



