721L 
muscular coat of the bladder are the usual 
means by which the action of this viscus is 
promoted, It is possible that, as with the rec- 
tum, under peculiar circumstances the physical 
stimulus acting reflexly on the muscular fibres 
themselves may come in aid of that of volition ; 
but such a mode of action is not the ordinary 
one. A line of argument similar to that which 
disproves the reflex nature of the action of 
the sphineter ani tells equally against that of the 
sphincter vesice. Were the action of this mus- 
cle reflex, it ought to remain perfect when- 
ever a sufficiently large segment of the cord 
remains in connexion with the bladder. “Now 
when the spinal cord is severed in any region 
so as to occasion paralysis of the lower extre- 
mities, there is almost always incontinence of 
urine from the removal of voluntary influence 
from the sphincter vesice : such ought not to 
be the case, if Dr. Hall’s views were correct. 
Respecting the cardia and the valvula coli, I 
shall only remark that the evidence of reflex 
action is extremely defective. The cardia, in- 
deed, has no sphincter; it is closed by the 
lower circular fibres of the esophagus, which 
keep that canal in a contracted state by their 
tone or passive contraction, The pylorus is 
provided with a sphincter muscle of great 
power, which closes that orifice by its passive 
contraction, and which in animals recently 
killed will continue to close the orifice as long 
as the muscle retains its tone. If an animal 
be killed during stomach digestion, the stomach 
may be removed, and yet the pylorus will retain 
the food in it even against gravity ; the cardia, 
if a sufficient portion of the c@sophagus be 
retained, will resist the escape of the food; 
but, from the absence of a true sphincter, to a 
much less degree than the pylorus. It is im- 
possible that, under these circumstances, there 
could be any reflex action, as the stomach is 
removed from its connection with the nervous 
centre. The valvula coli appears to act simply 
on mechanical principles. 
There is, I apprehend, no more evidence of 
the exclusively reflex nature of the acts of 
expulsion than of that of the acts of retention. 
The expulsion of the feces and that of the urine 
are voluntary acts, aided essentially by the con- 
tractile power of the muscular fibres of each vis- 
cus, and perhaps, under Pesala circumstances, 
by a physical excitant. Were this power reflex, 
the expulsion would be no doubt much more 
frequent and much less under control, and, 
therefore, productive of frequent serious incon- 
venience. The expulsion of perspiration is 
probably effécted by the simplest mechanical 
means, the newly secreted fluid pushing before 
it that which was previously formed. The 
expulsion of the semen does, indeed, exhibit 
the characters of a true reflex act; but here 
how marked is the physical stimulus, and how 
necessary that it should reach a certain point of 
excitement before the action of expulsion re- 
sponds to it!- As to the expulsion of the fatus 
in parturition, while I am willing to admit 
that the physical power of the cord excited by 
the sensitive nerves at the neck of the uterus 
may exercise some influence on the contrac- 
PHYSIOLOGY OF THE NERVOUS SYSTEM. 
tions of the uterus, it seems to me quite evi- 
dent that the actions of this organ are reflex 
only to a very slight degree. In the first place, 
anatomy teaches us that the muscular parts of 
the uterus have a very trifling connexion with 
the spinal cord; the nerves distributed, to it 
being few, and these only partially derived 
from the spinal cord. Secondly, | parturition 
may take place even when the spinal cord has 
been diseased or divided so as to cut off its in- 
fluence upon the inferior half of the. body, 
Thirdly, it has lately been ascertained that in 
women under the influence of ether, the act.of 
parturition may take place with vigour, 
the nervous power have been very i 
depressed by the influence of that agent... 
Ihe immediate agent of expulsion in, defe+ 
cation, micturition, and parturition is the inhe- 
rent contractility of the muscular coat of the 
proper organ. Being hollow muscles, the sti+ 
mulus of distension is well, adapted to excite 
them to contract. The will exercises consider- 
able power in defecation and micturition, 
both upon the muscular fibres of the viscera 
themselves, and on the abdominal. muscles, 
In parturition the voluntary contraction of these 
latter muscles may give some assistance, but 
the main force of expulsion is due to the con-— 
traction of the uterine muscular fibres... In all 
the three actions, however, the influence of the 
muscular fibres of the viscera Fespenreas as 
gaged may be materially promoted by the.con- 
tractions of the abdominal muscles, which: 
ly voluntary and partly reflex, being excited 
y the pressure of the mass to be expelled 
the sensitive nerves in the ceighboureell 
which, acting on the spinal cord, stimulate the 
muscular nerves, and through them cause the 
muscles they supply to contract, in harmony 
with the muscular tunic of the expelling viscu 
rectum, bladder, or uterus, as the case may be. 
I may here remark, that whilst it is suf 
ciently evident that expulsion of the semends 4 
physical or reflex act, it cannot be admitted 
that erection of the penis is essentially so in its 
ordinary mode of production. This act is on 
of emotion—a simple emotion.of the mind is 
sufficient to develope it: it may, however, bi 
developed by the application. of a stimulus t 
the penis or scrotum, when it clearly partak 
of the character of a reflex act, although eve 
under these circumstances it would be ineo 
rect to say that emotion had no influence in 
production. It is well known, however, 
in cases where the spinal cord has been sever 
injured, severed indeed, by fracture and 
placement of some of the vertebra, erection 
the penis may be produced, although the ¢ 
is insensible, and the influence of the mind « 
the lower half of the body is suspended 
that even a slight stimulus, as the friction 
the bedclothes, or the introduction of a cath 
is sufficient for this purpose. . This is clea 
purely reflex act, wholly independent o 
tion or emotion; but it may be likewise p 
duced or kept up by the irritated state of 
cord itself. The painful erection of the per 
called chordee, which occurs in cases of infi 
matory gonorrhea, is partly a reflex pheno 
