22 ANALYTIC SECT. III. . 
SECTION III. 
Irritability. 
xxx. By irritability is here understood the 
expansion and contraction of the soft fibrous 
structure of the human body. Haller, in oppo- 
sition to Glisson and Gorter, confined its signifi- 
cation to muscular contraction. But irritability, 
in the extended sense of the word, comprehends 
the motions of the skin, muscles, viscera, glands, 
and vascular system. The subject of irritability 
has been not a little obscured by the method in 
which it has been usually investigated: to kill an 
animal, and apply chemical agents to its nerves 
and muscles, and to employ the consequences of 
these applications to the explanation of vitality, 
must lead to false conclusions. The muscles are 
thus subjected to an influence different from 
the vital force, and different consequences arise 
from it. 
xxx. In the view of irritability which I am 
about to offer, I shall, for the most part, consider 
all the organs in which it is situated, in their 
entire state, and under the influence of the vital 
