468 
ERO RE 
[March 15, 1883 
ofthe cerebral motor areas, therefore, does not exercise 
a definite inhibitory action upon reflexes, but does under 
certain conditions markedly increase them, one might 
expect that their removal would diminish reflex action. 
Such a diminution actually occurs when they are destroyed 
in disease, but when the brain is removed layer by layer 
in operations upon animals, it is usually found that the 
reflex increases in proportion to the quantity removed. 
When the whole brain is removed, the reflex action is 
greater than when it is present, and as the cord is cut 
away layer by layer, the excitability of the seg nent below 
appears to be increased ; each layer, as has already been 
mentioned, appearing to have an inhibitory influence on 
the one below it. But this is not always the case, because 
we sometimes find on removal of the various parts of the 
brain or of the spinal cord that the section completely 
abolishes reflex action for the time. 
We are accustomed frequently to cloak our ignorance 
of the true cause of this abolition by saying it is due to 
the shock of operation or something of that sort; but 
looking the facts fairly in the face, we find that some- 
times removal of the upper part of the brain or spinal cord 
causes increase and sometimes diminution of reflex-action 
in the parts below. At present we have no satisfactory 
explanation of this phenomenon, but if we suppose in the 
one case the nervous matter to have been removed in 
such a way as to cause an interference of the stimuli 
passing along from cell to cell, and in the other to 
cause a coincidence, we can readily understand the 
occurrence of the two different conditions. Moreover, 
we have said several times, that inhibition or stimu- 
lation are only relative conditions depending on the 
length of path along which the stimulus has to travel, and 
the rapidity with which it travels. The length of path 
remaining the same, the occurrence of stimulation or 
inhibition depends upon the rapidity of passage of the 
stimulus. The same length of path which is just suffi- 
cient to throw successive impulses of a slowly travelling 
stimulation half a wave-length behind the other, and pro- 
duce inhibition, may be just sufficient to throw the vibra- 
tions of another more rapidly transmitted stimulus a 
whole wave-length behind, and produce increased instead 
of diminished action. 
If the hypothesis that inhibition is produced by inter- 
ference be true, we shall be able to test it by seeing 
whether stimulation of certain nerves which, under the 
ordinary conditions produce inhibition, do so when the 
rate of transmission of nervous impulses is altered. The 
length of path being the same, if we alter the rapi- 
dity of transmission it is probable that as the rapidity 
diminishes, the inhibition will be converted into stimula- 
tion, again possibly passing into inhibition, according as 
the stimuli, which we normally suppose to be half a wave- 
length behind each other, are thrown a whole wave- 
length, or a wave-length and a half behind each other. 
At a certain period, also, the waves of stimulation will be 
neither a whole nor a half wave-length behind each 
other, but the fraction of a wave-length. In such cases 
we shall neither have constant coincidence, nor constant 
interference, but we shall have rhythmical coincidence and 
rhythmical interference, the result of which will be that 
we shall neither get constant motion, nor constant arrest 
of motion, but alternate motion and rest. In other words 
we shall neither have complete rest nor tonic contractions, 
but intermittent or clonic contractions. Now this con- 
dition is exactly what we do find when one sciatic of a 
frog is irritated twenty-four hours after it has been exposed. 
We have already mentioned that when irritated imme- 
diately after exposure it had the effect simply of abolishing 
reflex action in the other leg; but the same irritation 
applied in the same manner after many hours, instead of 
causing arrest in the other leg, causes clonic convulsions.* 
This occurrence is very hard to explain on the ordinary 
1 Nothnagel, Centralblatt f. d. med. Wiss. March 28, 1869, p. 211. 
hypothesis of separate and distinct inhibitory centres, but 
it agrees perfectly with the hypothesis that inhibition and 
stimulation are merely relative conditions. 
I have repeated Nothnagel’s experiments, but I have 
not got the same results. Irritation of the sciatic nerve 
indeed caused a certain diminution in reflex at first, but’ 
irritation after twenty-four hours caused no clonic con- 
vulsions, it merely appeared somewhat to stimulate reflex 
action in the other leg. The reason of this discrepancy 
in our results is probably that the temperature was dif- 
ferent in the two cases. Nothnagel’s results were pub- 
lished in March, and his experiments were probably 
performed during cold weather, while mine were done 
during very mild weather. If the effects which he noticed 
were due to definite inhibitory centres in the spinal 
cord similar experiments should have had similar results 
in his hands and mine __ If on the other hand the effects 
simply depend on the rate of the transmission of nervous 
impulses it is easy to understand why the results were 
different in the two cases. 
There are also certain pbenomena connected with the 
action of drugs on the spinal cord which are almost 
inexplicable on the ordinary hypothesis, but which are 
readily explained on that of interference. Thus bella- 
donna when given to frogs causes gradually increasing 
weakness of respiration and movement, until at length 
voluntary and respiratory movements are entirely abo- 
lished, and the afferent and efferent nerves are greatly 
weakened. Later still, both afferent and efferent nerves 
are completely paralysed, and the only sign of vitality is 
an occasional and hardly perceptible beat of the heart 
and retention of irritability in the striated muscles. The 
animal appears to be dead, and was believed to be dead, 
until Fraser made the observation that if allowed to 
remain in this condition for four or five days, the apparent 
death passed away and was succeeded by a state of 
spinal excitement. The forearms passed from a state of 
complete flaccidity to one of rigid tonic contraction. The 
respiratory movements reappeared ; the cardiac action 
became stronger, and the posterior extremities extended, 
In this condition a touch upon the skin caused violent 
tetanus usually opisthotonic, lasting from two to ten 
seconds, and succeeded by a series of clonic spasms. A 
little later still the convulsions change their character and 
become emprosthotonic. These symptoms are due to the 
action of the poison upon the spinal cord itself, for they 
continue independently in the parts connected with each 
segment of the cord when it has been divided. 
This action may be imitated by a combination of a 
paralysing and exciting agent such as strychnia and 
methyl-strychnia. Fraser concludes that the effects of 
large doses of atropia just described are due to a com- 
bined stimulant and paralysing action of the substance on 
the cord, and that the difference in the relations of these 
effects to each other, which are seen in different species 
of animals, may be explained by this combination acting 
on special varieties of organisation. 
T. LAUDER BRUNTON 
(To be continued.) 
NOTES 
THE Queen has signified her intention of opening the 
International Fisheries Exhibition, at South Kensington, on 
Saturday, May 12. 
BARON NORDENSKJOLD writes to us that he has definitely 
settled to start for the interior from Auleitsivik Fjord on the 
west coast, and then, in September, to go round Cape Farewell 
along the east coast to the north. 
A Most interesting letter has been received at Kew Observa- 
tory from Mr, Cooksley, of Capt. Dawson’s expedition to Fort 
| Rae. They arrived on August 30, started the meteorological 
