721E 
herent in the medullary pulp of the nerves, and 
is not simply derived from the brain, but that 
a certain cohesion of the medullary pulp of 
the nerves is necessary for the developement 
of the vis nervosa, because if by compressing 
a nerve strongly we injure its medulla, so as 
to disturb the connection of its particles, the 
nervous force ceases in that part of the com- 
ressed nerve, nor are impressions propagated 
urther by it, nor if that part of the nerve be 
stimulated can sensation or motion be pro- 
duced. 
Although, he says, a nerve is necessary for 
sense and motion, it is not it alone which feels 
or moves ; it feels by the brain, which, when an 
impression made upon a nerve is conveyed to 
il, represents that impression to the mind; and 
a nerve causes motion by the muscle when an 
impression, communicated to the nerve, de- 
scends to the muscle and excites it to motion. 
He concludes thus: “ Par itaque nervi, in sensu 
et motu ciendo, est officium, nimirum im- 
ressionem stimuli recipere, et per totam suam 
ongitudinem celerrimé propagare, que dum 
ad cerebrum pervenit, sensus perceptionem 
causat, dum vero ad musculum, ejus contrac- 
tionem ciet.” 
Prochaska recognises the influence of the 
nerves upon the bloodvessels, and ascribes va- 
rious familiar phenomena to this influence, 
either excited by direct contact of the nerves 
of the part, or, if the nerves be indirectly 
affected through the brain (si isti nervi non 
immediate, sed mediante cerebro afficiantur). 
Thus he refers to redness of the skin of the 
face occasioned by exposure to a cold wind, 
redness of the conjunctiva caused by some irri- 
tant, erection of the nipple of the breast by 
titillation, erection of the penis by similar 
means or through mental emotion, blushing, 
&c. He puts forward the notion that the aug- 
mentation of the nervous force in any part 
causes an attraction of fluids to that part, as 
sealing-wax, when rubbed with cloth, becomes 
electrical and attracts various small particles. 
To a similar attraction of fluids he ascribes 
muscular action and many other phenomena, 
such as the menstrual Mux, the action of the 
iris, &c. He also discusses the question whe- 
ther the nerves have any power over the secre- 
tions, whether they contribute in any way to 
the production of animal heat, and how far 
they are necessary to nutrition. 
The fourth chapter describes the sensorium 
commune, its functions, and its seat. Lfere it 
is that Prochaska has put forward his views 
respecting reflex actions. External impres- 
sions, which are made upon sensitive nerves, 
are propagated with great velocity throughout 
their entire length to their origin, where, (to 
use his own phrase,) when they have arrived, 
ter are reflected according to a certain law, 
and pass into certain and responding (certos ac 
respondentes) motor nerves, by which again 
being very quickly propagated to muscles they 
excite certain and determinate movements. This 
place, he says, in which, as in a centre, nerves 
of sense and of motion meet and commu- 
nicate, and in which “the impressions of 
PHYSIOLOGY OF THE NERVOUS SYSTEM. 
sensitive nerves are reflected into motor nerves,” 
is called, by a term already received by most 
hysiologists, “ the sensorium commune.” 
laving referred to the various views of different 
physiologists as to the seat of the sensorium 
commune, he expresses his own opinion, that 
the sensorium commune, properly so. called, 
extends throughout the medulla oblongata, the 
crura cerebri and cerebelli, a part of the optic 
thalami, and the entire spinal cord,—in.a word, 
as far as the origins of the nerves extend. That 
the sensorium commune extends to the spinal 
cord is shown by those movements which con- 
tinue in animals after decapitation, which can- 
not be effected without the cooperation of — 
nerves which arise from the spinal cord; forif 
a decapitated frog be pricked, not only does it 
retract the stimulated part, but also it creeps, 
and leaps, which could not be done without the 
consentaneous action (absque consensu) of sen- 
sitive and motor nerves, the seat of which con- 
sentaneous action must be in the medulla spi- 
nalis, superstite sensorii communis parte, 
That Prochaska viewed these acts as purely 
physical in their nature, is apparent from his 
statement, that they take place under peculiar 
laws, written, as it were, by nature on the me- 
dullury pulp of the sensorium. The general 
law, however, whereby the sensorium com- 
mune reflects sensorial into motor impressions 
(impressiones sensorias in motorias reflectit) is 
our preservation; so that certain motor impres- 
sions should succeed to such external impres- 
sions as might be injurious to our bodies. In 
illustration he refers to certain acts of this 
such as, irritation of the mucous membrane o} 
the nose creating a violent act of expiration 
(sneezing) to expel the offending material from 
the nostril; the spasmodic closure of the glottis 
when “a particle of food or a drop of fi 
touches it, or the act of winking excited by 
the finger being brought close to the eye. 
Prochaska points out that these reflex a 
may take place with or without consciousr 
(vel anima inscia, vel vero anima conscif). — 
roof of this occurrence without conscious 
refers to certain acts which are observe 
apoplectic patients, to the convulsions of 
lepsy, and to certain actions in profound 
all those actions which occur in decapitat 
animals he refers to this class, and regards th 
as being regulated by the remaining porti 
the sensorium commune which is seated i 
spinal cord. “ Omnes iste actiones ex orge 
et physicis legibus, sensorio communi p 
fluunt, suntque, propterea, spontanez 
tomatice.” Actions, however, which the 
directs and moderates by its control, althou 
the sensorium commune may take its share 
producing them, may be called animal, % 
not automatic. lies / 
The second paragraph of this chapter: 
tains an excellent discussion of the qué 
how far the anastomoses of nerves contri 
their mutual action upon each other, or) 
that takes place only through the sen: 
commune. On this subject Prochaska adoy 
opinions of Whytt, who regarded the nervol 
centre as essential to these actions, and in” 
