
SECT. IX. PHYSIOLOGY. 83 
_ exci. Congestion of blood in the brain, often 
causes spasm of the muscles; it likewise fre- 
quently lessens the expansion of the heart, and 
consequently the quantity of blood in each 
pulsation. The abstraction of blood in such a 
case, restores the expansibility of the muscles, 
and increases the fulmess and strength of the 
- exci. These facts are so many direct proofs 
_ that the irritability of the heart and the whole 
- muscular system depends on the same causes, and 
is regulated by the same laws, the power of 
voluntary contraction alone being excepted. To 
these facts, indeed, may be opposed an abun- 
dance of authoritative assertions, but not one con- 
clusive apposite fact, that I know. Expansion of 
the muscles invariably precedes contraction; but 
with the greater number of physiologists, expan- 
sion has been nothing, and contraction every 
thing; hence has arisen a speculative physiology, 
which is neither amusing in itself, nor applicable 
to any earthly purpose but book-making. 
exci. The expansive force of the heart is very 
considerable, which may be ascertained by endea- 
vouring to prevent its expansion by compression 
with the hand. 
