9 
44 
INGA TATE 
[JANUARY 14, 1904 
and the fundamental principles of continuous current 
circuits mastered, it only remains to study alternating 
currents in the work of Messrs. Ryan, Norris and 
Hoxie. 
It is difficult to find anything particular to say of 
either of the three books, since each treats its subject 
in the manner which has become by now fairly 
familiar. They all possess certain merits not to be 
found in other books of a like kind, and certain defects 
which it is easy enough for the critic, who has only to 
read and not to write the book, to male much of. For 
example, Mr. Ashford proves Ohm’s law with electro- 
magnetic instruments, a logical mistake which it 
seems hopeless to eradicate from the text-book; Mr. 
Crapper does not prove it at all, but states that ‘‘ on 
account of its importance as the fundamental law of 
electrical measurements, it may be considered in the 
strictest sense a law of nature,’’ which seems to us 
rather a novel criterion for laws of nature. Mr. 
Crapper is also somewhat loose in his use _ of 
the terms force, energy, and power (‘‘ watts of 
energy,’’ for example, is an expression rather difficult 
to understand), and, indeed, in his definitions generally 
—an electrolyte is defined in one place as ‘ 
pound liquid with a metallic salt in solution.’’ These 
are, perhaps, slight defects, but one is justified in re- 
quiring more exactness of expression and more careful 
attention to detail in a text-book than one would think 
necessary in a lecture. The best justification that a 
text-book can claim is that it gives precision to the 
knowledge obtained experimentally in the laboratory. 
Mr. Ashford’s book is intended as a laboratory hand- | 
book ; in our own opinion the last thing wanted in a 
laboratory is a handbook. Such things are never to be 
found for the practical experiments the electrical 
engineer has to make when his days of school and 
college are over, and the greatest benefit of the labor- 
atory training is that it should train the student to 
walk alone. When experiments are so carefully de- 
scribed, and the results to be got and the conclusions 
to be drawn from them so plainly pointed out as in 
this book, the value of the experiment is greatly dis- 
counted, if the student even takes the trouble to carry 
it out properly. Mr. Crapper, on the other hand, errs 
by giving too much importance to the exercise class; 
if any student works through the enormous number 
of examples given in the book he will have done a 
great deal of arithmetic, but we doubt whether his 
engineering faculties will have benefited much. 
Messrs. Ryan, Norris and Hoxie proceed on what 
is, at any rate to English readers, the somewhat 
novel plan of plunging forthwith into the pheno- 
mena of alternating currents, ‘‘ from which the treat- 
ment continuous current phenomena follows 
naturally.’ This seems to us rather putting the cart 
before the horse, as we should certainly think the 
understanding of alternating currents must follow, 
and even then with difficulty, that of continuous current 
phenomena. This method involves also considerable 
mathematical knowledge in the student, and from this 
point of view alone seems scarcely the most suitable to 
adopt. 
In conclusion, we may repeat that fault-finding is 
NO. 1785, VOL. 69| 
of 
a com- | 
easy, and that these three books have much to recom- 
mend them. They are thoroughly up-to-date, and will 
compare very favourably with any three other books 
covering the same ground which we can call to mind. 
Their fault is not that they are bad text-books, but 
that they are good text-books. 
Maurice SOLOMON. 
THE PHYSIOLOGY OF MENTAL ACTIVITY: 
Etudes de Psychologie physiologique et pathologique. 
By E. Gley. Pp. viii+335. (Paris: Félix Alcanj 
1903.) Price 5 francs. 
WO-THIRDS of Prof. Gley’s book are devoted to 
a historical and critical review of our knowledge 
of the physiological changes that accompany intellec- 
tual activity. The writer gives a lucid account of his 
own contributions to the subject in chapters upon the 
relation of mental work to the cardiac, respiratory, 
vascular, excretory, and thermogenic mechanisms. 
He concludes that mental work is accompanied by in- 
creased rate of heart-beat (at least in the early stages 
of activity), by arterial constriction and increased peri- 
pheral resistance in the extra-cerebral circulation, and 
by active dilatation of the arterioles of the brain. No 
mention is made of the experiments and views of 
British physiologists in regard to the much-debated 
presence of a vaso-motor mechanism in the brain. 
The author bases his affirmative conclusion merely on. 
a study of the changes in form of the carotid pulse- 
curve during intellectual rest and activity. He is also 
inclined to believe that during intellectual activity the 
temperature of the brain rises slightly: Yet the 
evidence in favour of this view seems very far from 
adequate, for it has never been shown that the amount 
ot carbonic acid evolved is increased during the activity 
of nervous tissue, and we are powerless to decide 
whether the slight rise of cerebral temperature may 
not be due to other causes, e.g. to the increased blood 
supply to the brain, to diminution in loss of heat from 
the skin arising from the already mentioned peripheral 
vascular constriction. To cerebral metabolism the 
author also attributes the increase of calcium salts in 
the urine during intellectual activity. This increase 
is said to be accompanied by more abundant excretion 
of urine and of magnesium salts and phosphoric acid. 
Throughout the book Prof. Gley does not attempt 
to veil his intention to find analogies between cerebral 
and glandular activity, but a priori views, however 
excellent, are of little real avail in the solution of such 
an unusually difficult problem. There is, indeed, one 
complicating factor which is invariably neglected by 
physiologists, to which attention may be directed here. 
It is now generally believed that no mental process is 
possible without the simultaneous production of 
efferent impulses—in other words, thoughts must ex- 
press themselves in muscular activity. Even if this 
maxim exaggerates the truth, there can be no doubt 
that, as a rule, active intellectual efforts pass over 
into, and to some extent manifest themselves as, 
muscular contractions. These contractions may 
appear as vaso-motor changes or as involuntary move- 
ments, and they are largely responsible, at least when 
