Feb. 9, 1882 | 
NATURE 
335 
essay, which is on “Elementary Instruction in Physio- 
> logy? Thus— 
“The saying that a little knowledge is a dangerous 
thing is, to my mind, a very dangerous adage. If know- 
ledge is real and genuine I do not believe that it is other 
than a very valuable possession, however infinitesimal its 
quantity may be. Indeed, if a little knowledge is dan- 
gerous, where is the man who has so much as to be out of 
danger?” 
If the life-long labours of the greatest physiologist of 
his age—William Harvey—had revealed to him a tenth 
part of the knowledge which may now be made sound 
and real to our boys and girls “he would have loomed 
upon the seventeenth century as a sort of intellectual 
portent.” 
The address on “ Joseph Priestley” is an exceedingly 
interesting biographical and historical sketch, and is fol- 
lowed by the essay on “ The Method of Zadig,” which, 
from having been so recently published in the Wevefeenth 
Century, will be fresh in the memory of most readers. 
The lecture on “The Border Territory between the 
Animal and the Vegetable Kingdoms ” was delivered at 
the Royal Institution in January, 1876, and is a masterly 
piece of biological exposition, which “tends to the con- 
clusion that the difference between animal and plant is 
one of degree rather than of kind; and that the problem 
whether, in a given case, an organism is an animal or a 
plant, may be essentially insoluble.”’ 
The essay “On certain Errors respecting the Structure 
of the Heart attributed to Aristotle,” having been origin- 
ally published in NATURE (vol. xxi. p. 1) need not detain 
us now; we shall therefore pass on to the next in the 
series, and the one which has excited more interest and 
discussion than any of the others. This is the Evening 
Lecture before the British Association in 1874, “ On the 
Hypothesis that Animals are Conscious Automata ;” and 
both as regards the interest of its subject-matter and the 
logical precision with which the argument is stated, we 
think that it deserves to be considered the most important 
essay in the series. 
It is now universally known what the argument is, and 
how with irrefragable sequence it leads us to the conclu- 
sion that— 
“Consciousness would appear to be related to the 
mechanism of the body simply as a collateral product of 
its working, and to be as completely without any power 
of modifying that working as the steam-whistle which 
accompanies the work of a locomotive engine is without 
influence upon its machinery.” 
There can be no doubt that the logic by which this 
conclusion is reached is everywhere intact ; but there is 
one important criticism to which the “hypothesis” in 
question is open, and which, as it has not we believe been 
hitherto clearly advanced, we may briefly state. 
The hypothesis rests on the fact that there is a constant 
parallelism between cerebral processes and mental pro- 
cesses, and as this fact cannot be attributed to accident 
and is not attributed by the hypothesis of automatism to 
any pre-established harmony, there remains only the 
supposition that the true processes are in some way inti- 
mately associated. Some intimate association between 
neurosis and psychosis being thus accepted as a fact by 
the hypothesis of automatism, the whole question which 
this hypothesis raises may be briefly put thus :—If the 
stream of mental activity were withdrawn, could the 
stream of cerebral activity with which it is now asso- 
ciated continue in exactly the same way, or could it not? 
In other words, is the constant relation which now sub- 
sists between the two processes necessary or unnecessary 
to the occurrence of the latter? The hypothesis of auto- 
matism virtually answers that the relation is unnecessary, 
and this on the ground of its being inconceivable that it 
should be necessary. But now let us ask, Is it any more 
conceivable that this relation should be unnecessary ? 
Certainly not, because the inconceivability resides in the 
fact of there being some relation, and is not affected 
whether we choose to regard the character of this relation 
as necessary or unnecessary. We may try in thought to 
refine this relation, and to re-refine it again and again, 
until we conceive of mental processes as mere indices cf 
corresponding neural processes; but so long as we 
accept the belief that there is amy one point of contact 
between these two sets of processes, so long are we in 
the presence of just the same difficulty as when we 
started. Having driven the soul into some minute 
pineal gland of unnecessary relation, we find after all 
that we have gained nothing on the side of conceiva- 
bility ; we find it is no more easy to understand the soul 
as located in this little gland of unnecessary relation, 
than to understand it as distributed over the whole brain- 
work of intimate and necessary relation. The hypothesis 
of automatism would thus appear to contain the elements 
of its own destruction. For while accepting a fact which 
renders either the affirmation or the negation of the 
hypothesis alike inconceivable—viz. the fact of there 
being @ connection between neurosis and psychosis—it 
nevertheless proceeds to choose one of these alternatives 
in preference to the other; and this on the sole ground 
of inconceivability. 
Of course in advancing this criticism we are not our- 
selves arguing for any theory. We are merely observing 
that as in the theory of automatism there is, er hypothes?, 
some connection between neurosis and psychosis which is 
of a nature not merely unknown but inconceivable, the 
theory can have no right to affirm, or even to infer, that 
this connection is unnecessary ; and common sense will, 
therefore, have as much reason as ever to disbelieve that 
if consciousness had never appeared upon the scene of 
life, railway trains would now have been running filled 
with mindless passengers, and telephones would have 
been invented by brains that could not think, to speak to 
ears that could not hear. Thus, until it is shown who 
or what it is that blows the whistle of consciousness 
in the simile of the steam-engine, we must conclude that 
the hypothesis of conscious automatism is nothing more 
than an emphatic re-statement of the truth, that the rela- 
tion between body and mind is a relation which has so 
far proved inconceivable." 
Essay X. is on “‘ Sensation and the Unity of Structure 
of Sensiferous Organs.” It presents a 7ésumé of some of 
the older theories of sensation, and a clear statement of 
the modern generalisation that “ whatever be the apparent 
diversities among the sensiferous apparatus, they share 
certain common characters,’ &c. 
T Tt is no answer to say that the dvazz blows this whistle, for even if a 
causal relation is assumed, it is no more concezvadle that this should extend 
from neurosis to psychosis than that it should extend from psychosis to 
neurosis. 
