212 PHYSIOLOGY CHAP. 



with the help of a manometer communicating with a cavity in the 

 dead heart, to have observed a diminution of pressure, so soon as 

 they injected the walls of the heart from the coronary artery ; but 

 Oehl, on repeating the experiment, found exactly the contrary, i.e. 

 increase of pressure within the heart, so soon as the pressure was 

 strongly augmented in the coronary vessels. 



This contradiction between the results of such experienced 

 experimenters shows, without reference to other arguments that 

 might be brought forward, and have been adduced by Oehl, that 

 Briicke's theory is quite inadequate to explain diastolic aspiration. 



(c) Gaule (1886) suggested 'that the negative pressure in the 

 ventricle, which he determined with Goltz by means of a minimum 

 manometer, depended on the dilatation of the aortic orifice after 

 closure of the semilunar valves at the commencement of diastole. 

 Since the aorta is connected with the fibrous ring from which the 

 muscle fibres of the ventricle originate, it follows that the ventri- 

 cular cavity must dilate at the moment when the ring becomes 

 distended, producing a negative pressure. Both Minck (1890) and 

 Krehl (1891) proposed this hypothesis. 



But even if it is undeniable that when the aortic orifice dilates, 

 the conus arteriosus which lies below, and is in a certain sense one 

 with it, dilates also, it does not follow that this condition occurs at 

 the beginning of diastole, and can explain the diastolic aspiration. 

 The maximum of pressure and dilatation in the bulbus aortae 

 must obviously be reached during the systolic efflux, and not at 

 the commencement of diastole. " At the first outpouring of the 

 systolic stream," as Ceradini says, " the bulbous portion of the 

 artery (aorta or pulmonary) dilates, so that each of its diameters 

 increases by about one-fifth ; the walls of the sinus Valsalvae are 

 better able to resist the impact, yet they, too, show a very consider- 

 able dilatation, owing to the distension of the valvular membranes, 

 whose free borders become straight at the first onset." 



At the commencement of diastole, on the other hand, the 

 valves are already closed and bulge towards the conus arteriosus, 

 so as to diminish its capacity, presenting with their united margins 

 'the figure of the sides of a tetrahedron, the apex of which, built 

 up of the three coincident corpora Arantii, falls on its vertical 

 axis, and is inverted downward towards the hollow of the 

 conus arteriosus. "The insertion of the valvular borders," says 

 Ceradini, " are externally recognisable at the points of contact of 

 the ellipsoid formed by the sinus Valsalvae, by a conspicuous 

 depression, which is visible at the arterial wall at the first onset of 

 diastole, in consequence of the sudden distension of the semilunar 

 membranes." 



Gaule's explanation accordingly fails to explain the diastolic 

 aspiration. 



(d} The oldest hypothesis in explanation of the active diastole 





