SECT. XV, PHYSIOLOGY. 121 
also the dilatation of the heart; and, in a word, 
that kind of active vital expansibility, of which 
certain parts appear susceptible. In acknowledg- 
ing the reality of this sort of vital motion, I avow 
that I have as yet no clear or precise ideas on the 
the relations which unite it with other kinds of 
motion, nor on the differences which distinguish 
it from them.”—Bichat, p. 105, Sur la Vie et 
la Mort.” ; 
CCLxxxv. There is great ingenuousness in these 
remarks; this celebrated author saw clearly that 
the motion of the iris, the heart, and the corpera 
cavernosa, directly contradicted his doctrine of 
contractilité; but in place of casting about to 
reconcile the contradiction, he openly confessed, 
that he did not understand the subject. It is 
rather strange, that he did not assimilate the 
expansion of these organs with his “ Extensibilité 
Animale, and Organique,” as he would have thus 
represented the animal economy as in harmony 
with itself. | 
ccLxxxvi. As the irritability of the iris is very 
great, the size of the pupil depends entirely on 
its degree of expansion. ‘The iris derives its vital 
force from the optic nerve, for it loses its expan- 
sibility when this nerve is destroyed, compressed, 
or paralyzed. The whole nervous system has its 
action supported by the blood ; but various parts 
of it are so organized, that they are modified by 
| Q 
