MR, MAYHEW ON PHYSIOLOGY OF THE HEART. 267 
But now comes Mr. Mayhew’s chef d’ oeuvre — his discovery 
of a new fact with regard to the tricuspid and mitral valves. 
He states that, when the auricles are contracted they form 
the roofs of the ventricles, and thus render the tricuspid and 
mitral valves useless as a separation between the auricles and 
ventricles. He denies, however, that the valves are quite 
functionless; for, he thinks that during the contraction of 
the ventricles, the fleshy pillars lessen in size, and so tighten 
the cords as to pull the walls of the cavities up, and thus to 
cause the expulsion of their contents into the aorta and 
pulmonary artery. The contents of the ventricles are, 
according to him, prevented from passing into the 
auricles, on account of these cavities being already filled 
with blood. 
Mr. May hew appears to think, that, by the contraction of 
the muscular fibres of the ventricles, the walls of these cavi- 
ties become thinner, and that the carneag columnae are thus 
lessened in size. Now, it is plain that, on the contrary, the 
walls will increase in thickness as they shorten in length, 
and that the fleshy pillars will also be more clearly defined. 
This is distinctly stated by Dr. Carpenter (Human Physiology, 
p. 478). The cordae tendineae and valves, then, which during 
the dilatation of the ventricle are kept comparatively tense, be- 
come slackened by the shortening of t he ventricular cavity, and 
when the blood is propelled up against them, the valves will be 
driven into the auric.ulo-ventricular opening, and the cordae 
tendineae rendered tight. This tightening of the cords thus 
appears to be the effect of the expulsion of the blood from 
the ventricles, and not its cause , as Mr. May hew has vainly 
endeavoured to show : for, the muscular contraction of the 
ventricles is enough to account for the expulsion of their con- 
tents, without believing that the cords are sufficiently pow- 
erful to communicate an impulse to the thick walls of the 
cavities. 
Again, to say that the presence of fluid in the auricle is 
sufficient to resist the strong impulse of the current of blood 
from the ventricle, without regurgitating, is quite preposte- 
rous. Indeed, in the diseased condition of the valves in 
which they are so corrugated by partial ossification, as to be 
unable to flap up into the auriculo-ventricular opening, there 
is sufficient evidence to show the fallacy of Mr. Mayhew’s 
view. For, in that condition a murmur, caused by the re- 
gurgitation of blood, is well known to acompany the first 
sound of the heart. This disorder of function appears to be 
identical with that which Mr. Mayhew supposes to be the 
natural action of the auriculo-ventricular valves, and shows 
