182 
MR. YOUATT’s veterinary LECTURES. 
Theory of the Communication of Nervous Influence. —You will 
find a beautiful explanation ot the flow or communication of 
nervous influence to the various parts of the system, in that 
admirable work by Dr. Mason Good, his Study of Medicine f 
a work that should find a place in your libraries, as yielding to 
none in a clear, natural, and interesting explication of the prin¬ 
ciples of human pathology, and physiology too. I will use his 
own language:—‘‘We have had frequent occasions of shewing 
that the nervous pov\’er which supplies the muscular fibres is 
communicated, not strictly speaking in a continuous tenour, 
but in minute and successive jets; so that the course of it is 
alternately broken and renewed by a series of fine and impercep¬ 
tible oscillations. In a state of health and vigour this succession 
of influx and pause is perfectly regular and uniform ; and hence 
whatever movements result from it will partake of the same uni¬ 
formity, and appear to be one continued line of action instead of 
a successive series. But as soon as ever the harmonious alterna¬ 
tion through which the nervous power is thus supplied is inter¬ 
fered with, the oscillations become manifest; the apparently 
uniform current is diverted into a tremulous undulation*; and the 
muscular exertion to which it gives rise, instead of being seem¬ 
ingly one and undivided, is sensibly multiplied into hundreds.” 
Adopted to illustrate the Diseases of the Spinal Chord. —I 
would scarcely go so far as this excellent writer has done, when 
he says that ‘‘ the truth of this theory is shewn or proved but 
there are so many circumstances which give an air of probability 
to it, such as the firmness of the sound and healthy limb—the 
trembling of the hand fatigued by labour—the shaking palsy of 
old age—the agitation of every limb when the animal is violently 
excited—and, above all, this theory furnishes me with so intelli¬ 
gible an illustration of the diseases of the nervous system, that I 
shall adopt it, for the present purpose at least. 
Illustration of the Diseases of the Spinal Chord. —“In health, 
the succession of influx and pause is perfectly regular and 
uniform, and the motions resulting from it appear to be one con¬ 
tinued line of action,” energetic in proportion to the degree of 
nervous influence bestowed ; but I can conceive of some diseased 
state of the sensorial system in which the nervous energy shall 
rush on with unusual violence and without pause, and in defiance 
of the will. If one limb only is affected, we have rigid spasm, of 
that limb ; if it is a general affection, we have tetanus. If the 
pauses or relaxations are too protracted, then, from the accumu¬ 
lation of nervous power, the next jet has more than usual 
strength, and we have shivering and trembling. If the protrac¬ 
tion is more considerable, and confined to one set of muscles, we 
