406 ANIMAL PHYSIOLOGY. 
The share which the elasticity of the arteries takes in 
forcing on the blood when the heart ceases, and the contraction 
of the muscular coat of these vessels, especially the smaller, 
must not be left out of the account in explaining the phenom- 
ena of asphyxia and the post-mortem appearances, 
Pathological—The importance of being practically as well as 
theoretically acquainted with the facts of asphyxia is very great. 
The appearance of the heart and venous system gives une- 
quivocal evidence as to the mode of death in any case of as- 
phyxia; and the contrast between the heart of an animal bled 
to death, or that has died of a lingering disease, and one 
drowned, hanged, or otherwise asphyxiated, is extreme. 
We strongly recommend the student to asphyxiate some 
small mammal placed under the influence of an anesthetic, 
and to note the phenomena, preferably with the chest opened ; 
and to follow up these observations by others after the onset 
of rigor mortis. 
PECULIAR RESPIRATORY MOVEMENTS. 
Though at first sight these seem so different, and are so as 
regards acts of expression, yet from the respiratory point of 
view they resemble each other closely; they are all reflex, 
. and, of course, involuntary. Many of them have a common 
purpose, either the better to ventilate the lungs, to clear them 
of foreign bodies, or to prevent their ingress. 
Coughing, in which such a purpose is evident, is made up of 
several expiratory efforts preceded by an inspiratory act. The 
afferent nerve is usually the vagus or laryngeal, but may be 
one or more of several others. 
The glottis presents characteristic appearances, being closed 
and then opened suddenly, the mouth being kept open. 
Coughing is often induced in attempting to examine the ear 
with instruments. (Reflex act.) 
Laughing is very similar to the last, so far as the behavior 
of the glottis is concerned, though it usually acts more rapidly, 
of course. Several expirations follow a deep inspiration. 
Crying is essentially the same as laughing, but the facial 
expression is different, and the lachrymal gland functions exces- 
sively, though with some persons this occurs during laughter 
also, 
Sobbing is made up of a series of inspirations, in which the 
glottis is partially closed, followed by a deep expiration. 
