760 
liarly called heartburn; and in is, or water- 
brash, the amount of liquid which suddenly 
enters the mouth is often very considerable. 
This inverted action of the esophagus admits 
of a ready explanation. By the contraction 
of the muscular fibres of the stomach a portion 
of liquid is expelled into the lower extremity 
of the esophagus; here it immediately excites 
contraction of the muscular fibres which sur- 
round it, and being prevented from again en- 
tering the stomach by the momentary continu- 
ance of the same effort which has expelled it 
into the esophagus, it must necessarily pass 
into the relaxed portion of the tube immedi- 
ately above; and thus, by the contraction of 
successive portions of the tube, the liquid soon 
reaches the te In ruminants, the greater 
portion of the food is returned from the sto- 
mach to the mouth by this inverted action of 
the esophagus.’ During the action of vomiting 
’ there is an inverted action of the esophagus in 
addition to the propulsive effort arising from 
the contraction of the stomach and abdominal 
muscles. 
We have now to point out the precise mode 
in which these contractions are induced, to 
explain the intermediate links between the ap- 
lication of a stimulus to the mucous mem- 
rane and the occurrence of the muscular con- 
traction. In the first place, unless we swallow 
a very large or-a very hot morsel of food, no 
sensation attends its passage along the cso- 
phagus. After the food has passed that portion 
of the pharynx upon which the glosso-pha- 
ryngeal nerve is distributed, we cease to be con- 
scious of its presence; and again, when a bitter 
liquid is eructated from the stomach, it pro- 
duces no sensation of taste until it reaches the 
same point. As the passage of food along the 
cesophagus is unattended by sensation, so is it 
uninfluenced by volition. We cannot by any 
effort of the will perform the action of deglu- 
tition unless we bring a portion of food, or a 
liquid (as the saliva), into contact with the pha- 
rynx, by means of which the action of the parts 
may be excited. Again, no effort of the will 
can arrest the process of deglutition after the 
food has entered the esophagus, and if a liquid 
be made to pass into the pharynx of a person 
in whom the exercise of volition is suspended by 
a fit of apoplexy, deglutition is performed in a 
manner almost as perfect as bya person in health. 
An apparent exception to the general rule that 
‘the movements of the cesophagus are beyond 
the control of the will is afforded by the very 
rare examples of persons possessing the power 
of rumination. A voluntary power over the: 
cesophagus, however, appears by no means neces- 
sary to account for this. It probably depends 
on the possession of an unusual degree of vo- 
luntary power over the movements of the sto- 
mach, and especially of its cardiac orifice, by 
means of which the contents of the stomach 
can be expelled at will into the inferior extre- 
mity of the esophagus, and thus are brought 
within the influence of its involuntary move- 
ments. Any one may satisfy himself that he 
possesses some degree of voluntary power 
over the cardiac orifice of the stomach, if after 
(ESOPHAGUS. 
swallowing a bottle of soda water he will — 
direct attention to the power which he pos- — 
sesses of preventing the sudden escape of gas 
from the stomach, and, on the contrary, of — 
increasing the propulsive effort probably by 
contracting the abdominal muscles. It is pro- 
bable that many persons might by practice 
acquire the power of rumination. Since the — 
contractions of the esophagus cannot be ex~ 
cited by volition, are they dependent on the 
direct stimulus of the muscular fibres by cor 
tact of the food, independently of the ner 
and of the nervous centres? ‘Phat this is 
the case is proved by an experiment performe 
by Dr. J. Reid.* He divided ina rabbit 
vagus nerve on each side above the cesophageal 
lexus, but below the ngeal ches. 
e animal received the food which was offered 
to it, and by a propulsive effort of the tong 
and pharynx transmitted it to the cesoph 
which, having lost all power of contraction, 
remained passive, and became at | com: 
pletely distended and choked up b 1 
rials thrust into it from above. It is evide 
then that the cesophagus loses its power © 
contraction if we cut off its communicatior 
with the nervous centres. As we have b 
seen that the will is not the agent which deter 
mines the contractions of the esophagus, ther 
remains but oneexplanation of these movement: 
which is, that they belong to the class of refle 
actions. An impression made upon the mucot 
membrane of the cesophagus is communicate 
by the afferent nerves to the medulla oble 
gata, and thence an influence, the precise 
ture of which we are ignorant of, is reflec 
along the efferent nerves to the muscular fi 
of the part to which the stimulus was applic 
The only parts of this circle of actions wh 
we recognise by our senses are the applicat 
of the stimulus and the occurrence of the m 
cular contraction; but these are doubtless ¢ 
nected in the manner above mentioned. 
cesophagus receives both its excitor 
motor nerves from the pneumo-gastric; it” 
derives its nervous influence from that po 
of the nervous centre, namely, the m 
oblongata, which is the centre of the respi 
movements. Hence it will be seen that: 
in any case of disease of the nervous e¢ 
deglutition becomes seriously impaired, th 
much reason to fear that the moreimportant 
tion of respiration will soon become inv 
Abnormal anatomy.—The esophagus m 
viate from the normal state in form or in 
ture. In some cases malformation 
without obvious change of structure, b 
more common to find them combined. 
formation of the esophagus may be eithe 
genital or acquired. “9 
Congenital malformation.— It som 
happens that the esophagus is cor 
deficient, terminating above in a ¢ 
the inferior extremity of the pharynx 
minating in the same manner. This is 
associated with an imperfect developem 
the oral cavity and of the lower jaw, ti 
+4 
~? hale 
¥ 
7. 
* See the Edin. Med. and Surg. Jou 
7: 
