Fan. 5, 1882] 
NATURE 
215 
lesion of the cortex capable of being made the basis of 
reliable inductions. 
He has represented together on a series of figures of 
different aspects of the cerebral hemispheres the position 
and extent of the lesion recorded in each case; and he has 
carefully tabulated the symptoms observed, whether posi- 
tive or negative. In determining the functions of the 
parts he follows three methods mutually complementary. 
First, the method of negative instances ;—all the lesions 
being taken together in which a certain function was not 
affected. Secondly, the percentage method ;—the pro- 
portion of cases being indicated in which a certain region 
was diseased, and the relative frequency of the symptom 
in question. Thirdly, the method of positive instances, 
z.e, all the cases of disease in which a particular affection 
was observed ;—a method used mainly as an adjunct to 
the other methods, and not of itself of great force. By 
these methods he arrives at the determination of certain 
areas or centres which he terms adsolute, lesion of which 
always causes the same symptom. He defines more or 
less vaguely absolute centres for the upper and lower 
limbs more especially, In addition to the absolute areas 
he defines a number of ve/ative areas, or centres, for 
other movements, and different forms of sensibility ; the 
relative areas being those in which lesion does not always, 
but only freguently, cause affection of the function with 
which they are supposed to be in relation. 
The elaborate and carefully prepared figures which 
accompany the work indicate clearly the areas of latent 
lesions, as well as the position and extent of the absolute 
and relative areas which the author describes. 
Apart altogether from Prof. Exner’s deductions, one 
thing clearly brought out by the facts is the comparative 
impotence of the fortuitous experiments of disease as 
regards the determination with any degree of accuracy 
of the exact position and limits of any centre whatever. 
Prof. Exner has a deservedly high reputation as a physi- 
ologist, but the manner in which he has handled the 
facts of disease as set forth in this work is not one on 
which he can be congratulated. 
In his selection of instances he has excluded, without 
assigning valid reasons, many cases of the utmost im- 
portance ; and he has included, as instances of localised 
cortical disease, a large number of cerebral tumours, which 
by the general consent of pathologists, are excluded, 
owing to the indirect effect which tumours exert on other 
parts—effects which can never be estimated with any 
degree of certainty. In his meagre “ sammlung” of 168 
instances he has included over thirty cases of tumour, 
thereby introducing such a large percentage error as to 
vitiate the whole of his deductions however accurately 
they may be drawn from his premises. Causal relation- 
ship is too readily assumed when none is proved. Mere 
frequency of occurrence, on which alone he founds his 
peculiar notion of relative centres, by no means justifies 
the assumption of causal connection. These so-called 
relative areas are seen to be capable of destruction with- 
out discoverable symptoms, and the same region seems to 
play many parts, being indifferently a centre for the leg, 
or the arm, or the face, speech, sight, and so forth. Our 
author’s arguments in favour of his relative centres are in 
reality not more cogent than would be the inference that 
because injuries of the foot are frequently associated with 
disturbance of the circulation, therefore the foot is a 
relative centre of the circulation, whatever that may 
mean. If Prof. Exner’s localisation of relative centres 
had any foundation in fact, it would be nothing short of 
a veductio ad absurdum of the whole doctrine of localisa- 
tion. It is a marvel howa believer in localisation, as 
Prof. Exner declares himself, can see no incongruity or 
inconsistency in admitting that the absolute centre for 
the leg may also be a relative centre of vision. A con- 
sistent advocate of localisation might as well admit that 
the leg may frequently, relatively, or in some way or 
other be used as an organ of vision. 
Among other strange things in this book is the kind of 
evidence on which our author seeks to establish differ- 
ences between the hemispheres as to the extent and 
relation of the sensory and motor centres. In one of his 
figures of the left hemisphere there is an area in the 
occipital lobe so coloured as to indicate the position of 
an absolute centre for the arm, meaning that. lesion of 
this area causes paralysis of the arm in 100 per cent. of the 
cases. On referring to the evidence we find that the 100 
per cent. means only oe casé,a case, moreover, in which 
there was profound impairment of all the cerebral func- 
tions, and extensive lesion elsewhere of the left hemi- 
sphere, invading also what is generally recognised as the 
motor area proper. It is true that in his remarks on this 
case our author doubts its conclusiveness as regards the 
arm centre; but inasmuch as his instances give hima 
case of lesion of the same region in the right hemisphere 
without any symptoms whatever, he considers it beyond 
all doubt that this area has a more intimate relation with 
the upper extremity in the left hemisphere than in the 
right. It would be difficult to believe that this was 
written seriously, were it not that a similar style of 
reasoning is so prevalent throughout the book. Though 
Prof. Exner advocates the localisation of function in the 
cerebral hemispheres, the support he gives it is of the 
most equivocal description. DAVID FERRIER 
THE ROD IN INDIA 
The Rod in India. Being Hints how to obtain Sport, 
with Remarks on the Natural History of Fish, their 
Culture and Value, and Illustrations of Fish and Tackle. 
By H. S. Thomas, F.L.S., of the Madras Civil Service. 
Second Edition. (London: Hamilton, Adams, and 
Co., 1881.) 
HIS is a very much enlarged edition of a very excel- 
lent and pleasant book, the first edition of which 
appeared not quite eight years ago. The author asserts 
that there is as good fishing, in the angler’s sense, of course, 
of this word, to be had in India as in England; and to 
prove it we have this goodly royal octavo volume, of over 
400 pages and 25 plates. Now, though the fishing is 
good, it soon becomes apparent that it is something quite 
peculiar ; for though our author himself knew thoroughly 
well how to “circumvent” a trout in England, and had 
often done successful battle with the lordly salmon in 
more northern climes, yet at first he could make nothing 
of the Mahseer in India, and lost a frightful lot of time in 
learning the manners and the customs of this Oriental 
gentleman. The reader of this volume should not cer- 
