on Muscular Motion. 
2*5 
by no means stronger in proportion to the difference of effects 
they have to produce. We find, however, upon dissection, that 
the septurfi is almost wholly a portion of the left ventricle, 
which gives it a great superiority over the other, and makes it 
capable of performing the important office of supplying the 
body with blood. 
The left ventricle of the heart, detached from the other 
parts, is an oviform hollow muscle, but more pointed at its 
apex than the small end of a common egg. It is made up of 
two distinct sets of fibres, laid upon one another in the form of 
strata ; those which compose the outer set have their origin 
round thejroot of the aorta* and in a spiral manner surrounding 
the ventricle to its apex, or point, where they terminate, after 
having made a close half turn. The fibres of the inner set, or 
stratum, are similar to those of the outer, in their origin, in the 
mode of surrounding the cavity, and in their termination, but 
their direction is exactly the reverse ; they decussate the 
outer set in their whole course, and where the two sets termi- 
nate, they are both blended into one mass. There is an ad- 
vantage gained by this disposition of fibres over every other in 
the body, which adapts the ventricle so perfectly to its office, 
that it would almost appear impossible to construct it in any 
other way, so as to answer the purposes for which it is in- 
tended.. 
In this muscle, the fibres, by their spiral direction, are nearly 
one fourth part longer than the distance between the origin 
and insertion ; and, the action of the two. sets being in different 
directions, renders only one half the quantity of contraction 
in each fibre necessary, that would have been otherwise re- 
quired ; while the turn both sets make in opposite directions 
