436 
are suffering from want of proper attention, and what is 
of even more importance his health is failing with over- 
application to work. There is no alternative but to 
relinquish his favourite hobby, and he parts with his 
books and instruments for what little they will fetch. 
How many are there who have had this experience ? 
How many promising observers have left the science 
because it offers no pecuniary rewards or benefits such as 
other work commands? “Life is real, life is earnest”’; 
the telescope must be neglected for the ploughshare, and 
the solitary though withal happy hours of vigil must be 
given over to Morpheus! Many have realised all this, 
and though their names will never be known as astro- 
nomers, they have deserved as much credit for their dis- 
interested efforts as many others who have from more 
fortunate circumstances achieved eminence. 
It must be admitted that observers of the present day 
have many advantages over their predecessors, owing to 
the greater perfection and size of instruments and the 
conspicuous advances in the serial literature of the 
science. The latter has developed wonderfully during 
the last few years with such publications as The Obser- 
vatory, Copernicus, L’ Astronomie,. Sirius, Ciel et Terre, 
The Sidereal Messenger, &c. Formerly we had but the 
Astronomische Nachrichten, Wochenschrift fiir Astro- 
nomte, and Astronomical Register. This leads us to 
hope for a corresponding increase in the number of 
astronomical workers. 
It cannot be questioned that the essential direction of 
labour on the part of amateurs should be more of a syste- 
matic or methodical character than hitherto. A certain 
de,artment or definite work should be taken in hand and 
followed up persistently. Little good is likely to accrue 
from erratic work or from the hasty and necessarily in- 
complete examination of many different objects. Every 
observer has a leaning towards a speciality, and he 
should pursue this exclusively even to the absolute 
neglect of other departments. Astronomy offers such a 
large number and variety of objects that to attempt an 
investigation of more than a mere fragment will tax more’ 
than the energies of a lifetime. We would therefore 
recommend amateurs to apply themselves sedulously to 
such special branches as they may individually select, for 
the indiscriminate use of a telescope is to be deprecated 
on many grounds. W. F. DENNING 
ON THE NATURE OF INHIBITION, AND THE 
ACTION OF DRUGS UPON IT * 
Il. 
VULPIAN has observed that the excitability of 
* the lower parts of the spinal cord increases as the 
upper part is gradually shaved away, so that each layer 
of the cord appears to exercise an inhibitory action on 
the one below it. M. Brown-Séquard supposes that in 
each layer of the cerebro-spinal system there are both 
dynamogenic elements and inhibitory elements for the 
subjacent segments. 
We are, in fact, almost obliged to assume that each 
nerve-cell has two others connected with it, one of which 
has the function of increasing, and the other that of re- 
straining the function of the nerve-cell itself. 
Applying this same hypothesis to Newton’s rings, we 
would say that certain parts of the lens or of the glass 
plate possessed the property of interfering with the rays 
of light, or were inhibitory centres for them, Others 
again had the property of increasing the brightness, or 
were stimulating centres for them; and, moreover, that 
different parts of the lens or of the glass plate contained 
each its stimulating and inhibitory centres for different 
coloured rays. 
The multiplication of centres in the lens and glass 
plate soon becomes more than the imagination can well take 
* Continued from p, 42e. 
NATURE 
| March 8, 1883 
in; and we are at present almost precisely in the same 
condition regarding inhibitory and stimulating centres in 
the nervous system. 
As soon as we get rid of the idea that the darkness 
caused by the interference of the rays of light at certain 
points is due to some peculiar property inherent in the 
glass, and attribute the interference simply to the relation- 
ship between the waves of light and the distance they 
have to travel, the whole thing becomes perfectly simple, 
and the same is, I think, the case in regard to inhibition 
in the nervous system. 
Let us now take a few more examples of inhibition. 
We find in experiments with the frog’s foot exactly the 
same as on our own hand. Thus, when a little turpen- 
tine 1s placed upon the toes it excites a violent reflex, but 
if a little turpentine be injected under the skin of the 
same foot, the reflex is abolished.1 We find also that 
irritation applied to a limited region of the skin usually 
causes marked reflex, but if the same stimulus be applied 
to the sensory nerve supplying that region, the reflex is 
very much less.?_ In the cases just mentioned the irrita- 
tion is applied to sensory nerves of the same part of the 
body, and close together, and the explanation of its dif- 
ferent results is the same as that already given for the 
different effects of tickling and pressure. Different sensory 
nerves on the same side of the body, but at some distance 
from each other, will also cause inhibition of motor reflexes ; 
thus it has been shown by Schlosser * that simultaneous 
irritation of the skin over flexor and extensor surfaces 
will lessen reflex action. 
Some years ago I observed that frogs suspended by 
the fore-arms with cords, or tied with their bodies against 
a board, reacted less perfectly to stimulation of the 
foot by acid than a frog suspended by a single point, as in 
Tiirck’s method. Tarchanoff* has also observed that 
frogs held in the hand also respond less perfectly than 
when hung up; the gentle stimulation of the sensory 
nerves in the skin of the body appearing to exercise an 
inhibitory action over the reflex from the foot. 
The injection of acids or irritating solutions into the 
mouth ® or dorsal lymph sac ® also exercises an inhibitory 
action on reflexes from the foot. 
A similar effect is produced by irritating the sciatic 
nerve on one side by a Faradaic current, and applying a 
stimulus to the other foot. So long as the irritating cur- 
rent is passed through the sciatic nerve, no reflex move- 
ment can be elicited by stimulation of the other foot; 
but so soon as the Faradaic current stops, the reflex 
excitability again appears in the other foot.’ As this 
phenomenon occurs when the influence of the brain and 
upper part of the spinal cord has been destroyed by a 
section through the cord itself, the inhibition which occurs 
must be due to an action which takes place in the lower 
portion of the spinal cord. 
Stimulation of the nerves of special sense has also an 
inhibitory action on reflex movements. This we can 
readily see in ourselves, by observing our actions in the 
dark. If we touch something cold or wet, or if some- 
thing suddenly comes against our face, we give an in- 
voluntary start, sometimes almost a convulsive one. If, 
however, we were able to see, we should not give a start 
in the least when we touched a piece of wet soap, or 
when the end of a curtain suddenly came against our 
cheek. 
Without entering into the nervous mechanism through 
which sight effects this change in our actions, but only 
reducing it to its simplest form of expression, as we would 
* Richet, Muscles et Nerfs, Paris, 1882, p. 710. 
? Marshall Hall, Memoirs on the Nervous System, London, 1837, p. 48. 
3 Arch. of Physiol. 1880, p. 303, quoted by Richet, of. czt. 709. 
4+ Quoted by Richet, of. cft. p- 709. E - 
5 Setschenow, Physiologische Studien tiber die Hemmungsmechanismen 
fiir die Reflexthatigkeit des Riickenmarks im Gehirn des Frosches, Berlin, 
1863, Pp. 33- , 
6 Brunton and Pardington, St. Bartholomew's Hospital Reports, 1876 
Ds 155 
7 Nothnagel, Centralblatt d. med. Wiss. 1869. p. 21r. 
