108 WARFARE IN THE HUMAN BODY 



time to recuperate and gather energy, just as the vagus 

 when acting on an intestine has at first a slowing, " in- 

 hibitory " effect upon it, on what in the heart does the 

 vagus act ? Such a question leads to the consideration of 

 the diastolic mechanism, which seems so obscure that no 

 information whatever is to be obtained on the subject. 

 After consulting all books within my reach, the utmost I 

 have gathered is that the diastole is "an elastic rebound," 

 in some way connected with the columnce carnece. On 

 applying personally to certain authorities I was told it was 

 " a vital process." But so is the whole of life. The answer 

 answered nothing. We know that there is negative pres- 

 sure in the heart during diastole, so the old theory of the 

 passive diastole cannot stand. There are few, if any, 

 elastic connective-tissue fibres in the ventricle, whatever 

 there may be in the septum or the base. Is then the 

 diastole after all a muscular process in the sense that 

 certain layers contract ? One of our greatest authorities 

 tells me that there are no reasons for supposing that this is 

 so. The whole of the muscle layers seem adapted only for 

 the systole. It is true that in the systolic contraction there 

 appear to be torsion strains. If we adopt the view that 

 skeletal muscles are all systems, and that a single muscle 

 cannot exist, it is perhaps conceivable that certain layers of 

 cardiac muscle are stretched during the systolic torsion 

 contraction, and that the diastolic rebound is thus muscular. 

 Yet if the view is accepted that the mere lengthening of a 

 muscle is a positive and active process, and a change in 

 molecular order, which in some cases can do work, this 

 somewhat unlikely hypothesis can be dispensed with. We 

 have merely to inquire why in ordinary cases a lengthened 

 muscle is said to be relaxed, and why the positive cardiac 

 diastole, capable of producing a negative pressure, which 



