182 Dr. Williams on the active Power [March, 



the cavsfe were compressed, the inferior as near the diaphragm 

 as possible, and the superior, a little above its entrance into the 

 auricle. As the auricle was thus suddenly limited to the small 

 quantity of blood, that the vena azygos and the coronary veins 

 poured into it, it was expected that the blood, which remained 

 in the inferior cava between the compressed part and the auricle 

 would have been pumped out ; but no effect indicating a sudden 

 extraction of blood from the isolated portion of the inferior cava 

 could be perceived. Had the auricle or ventricle exercised the 

 function of active dilatation, it must have been discovered, for 

 the lungs were quiescent, and no muscular action, save that of 

 the heart itself, perplexed the observation. After the last systole 

 of the left ventricle has occurred, irregular and hurried, or flut- 

 tering contractions of the muscular fibres of the right ventricle take 

 place. When they have ceased, the right ventricle feels full and 

 soft, and the left feels contracted or collapsed. If now we open 

 one of the pulmonary veins near their termination in the auricle, 

 no expansion of the latter chamber or of the ventricle will take 

 place ; but as the residue of the blood in the pulmonary veins 

 drains into the ventricle, it imperceptibly fills, and its walls feel 

 softer to the touch. 



We shall now take into consideration the influence ascribed 

 to the active power of dilatation of the heart in the economy of 

 the circulation. In the first place, we shall inquire into the 

 nature of the power ; then compare its characteristic qualities 

 with the above phenomena ; afterwards we shall be able to 

 judge whether we have arrived at any facts capable of furthering 

 our acquaintance with the moving powers of the circulation. As 

 Dr. Wdson Philip is the last author on our subject whose writ- 

 ings I have perused, I shall take the liberty of quoting the fol- 

 lowing periods from his valuable essay,* so as to give my 

 leaders a correct statement of the ideas entertained by Dr. 

 Philip, as to the nature and the influence exercised by the inhe- 

 rent dilating power of the heart, and also the resilience of the 

 lungs. " What purpose then/' says Dr. Philip, " is served by 

 the dilating power of the ventricles increased by the tendency of 

 the lungs to collapse ? It favours the entrance of the blood sud- 

 denly propelled into it by the contraction of the auricle ; and 

 the degree of dilating power is well proportioned to this office. 

 Without this dilating power, the tendency of the ventricle would 

 be to remain in a state of collapse after the systole, and part of 

 the power of the auricle would be expended in dilating the ven- 

 tricle. Here, as in many other instances, both in man and the 

 inferior animals, we see nature saving the muscular by the sub- 

 stitution of the elastic power." In the last sentence we perceive 

 Dr. Philip recognizing elasticity to be the nature of the inherent 



" Some Observation* relating to the Powers of Circulation, &c. Medico-Chir. Trans. 

 Vol. xii. Part. II. 



