SECT. XVII. PHYSIOLOGY. 143 
the phrenic and great sympathetic nerves with 
those of the neck, accounts for the contraction of 
the muscles of the neck, when deep inspirations 
are required. 
ccctiv. The extent of dilatation of the chest 
corresponds always with the quantity of carbon 
in the blood. After long fasting, the breathing 
becomes short, and the inspirations small; but 
after eating, the breathing is quick, and the in- 
spirations deep. In the cold-blooded animals 
which pass the winter in a torpid state, their 
respiration is then often imperceptible, adapting 
itself to the scantiness of carbon in their blood. 
cccLy. The quicker the venous blood arrives 
at the lungs, the quicker are the inspirations. 
In inflammatory fevers, when the blood abounds 
with carbon, and the circulation is quick, the 
’ number and depth of the inspirations are always 
augmented. This physiological phenomenon is so 
obvious, as to have attracted the notice of the 
poet, and enters into his description of a sick 
walrior : 
«* His blood was fever’d, his breathing was deep.” 
cccLyv1. When the entrance of the air into the 
pulmonary cells is impeded, either by division of 
the par vagum, or pressure upon the trachea, 
violent contraction of the muscles of inspiration 
is equally produced. In whatever light the 
