2i 6 Mr. Ho me' s Lecture 
at the apex of the ventricle, fixes it and prevents lateral 
motion. 
In the action of the ventricle, two different effects are pro- 
duced ; the first brings the apex nearer to the basis, by which 
means the vis inertia of the blood will be overcome where the 
resistance is least, and a direction given to its motion in the 
course of the aorta ; the second brings the sides nearer each 
other, which will accelerate the motion of the blood already 
begun ; and the spiral direction of the fibres, will render the 
power which is applied, more uniform through the whole of 
that action, than it could have been made by any other known 
form of muscle ; the spiral action will also readily shut the val- 
vulas mitrales, while the apex is drawn up, which could only be 
effected by this particular construction. 
By this beautiful mechanism, which I have endeavoured to 
describe, the muscular fibres of tire left ventricle of the heart 
perform their office with a smaller quantity of contraction, 
compared to their length (although in themselves proportion- 
ally longer), than those of any other muscle in the body, and 
consequently produce a greater effect in a shorter time. 
The right ventricle is situated upon the outside of the left, 
with which it is firmly united ; it is not oviform in its shape, 
but triangular ; nor is it uniform in its structure, being made 
up of two portions, whose fibres have a very different distri- 
bution. 
The portion of this ventricle which makes a part of the 
septum of the heart, consists of only one set of fibres, similar 
in their direction to those of the stratum underneath, belong- 
ing to the left ventricle ; but from being considerably shorter, 
they are more oblique than the spiral ; and at the edge of the 
