64 
NATURE 
[SEPTEMBER 18, 1913 
dental ones; in some of the earlier investigations 
it appeared that the real conditional stimusus was 
given by the operator himself, by some peculiarity 
of odour or movements, and not at all by the 
stimulus which he believed he was employing. For 
this reason the animals are now <lways isolated in 
special rooms, which no person enters during the 
course of an experiment, all the conditions and 
observations being controlled from without by 
means of electrical or pneumatic arrangements. 
With regard to the inhibitory processes to which 
the reflexes are so subject, there may be distin- 
guished three kinds of inhibition. Firstly, we 
have the inhibition during sleep. Secondly, the 
inhibition by means of the arrival of other stimuli 
which have an inhibitory effect (external inhibi- 
tion), Thirdly, there is a variety which is called 
“internal inhibition.”” This is developed as a result 
of special relations between the conditional and un- 
conditional stimuli by means of which the parti- 
cular reflex has been prepared. When, for in- 
stance, the conditional 
stimulus is not followed 
by the customary uncon- 
ditional one for some 
time, it becomes con- 
verted into an inhibition. 
When in the developed 
reflex the conditional 
stimulus is not followed 
(or “confirmed ”’) by the 
unconditional one, the 
type of inhibition is called 
“extinction”’?; when in 
working out the reflex 
the unconditional stimu- 
lus only follows some 
minutes after the con- 
ditional, the inhibition 
which intervenes is called 
“retardation.”’ ‘“‘Condi- 
tional inhibition” is 
seen when the conditional 
stimulus, when ‘accom- 
panied by an_ indifferent 
stimulus, is not fol- 
lowed by the uncon- 
ditional stimulus; lastly, 
“differential inhibition ” in the fact that 
stimuli approaching closely to the conditional 
stimulus, and which at the commencement are 
effective, become eventually inactive. That all 
these phenomena are really due to inhibition can 
be shown by the fact that under appropriate con- 
ditions the inhibition may be removed, and the 
is seen 
effect manifested (‘‘ Loshemmung ”’). 
The powers of discrimination of the analysors 
are greatly increased during the development of 
the reflex, and the conditional stimulus becomes 
more and more limited and specialised until finally 
it corresponds to a very small part of the analysing 
mechanism. Experiments in which definite parts 
of the cerebral hemispheres have been removed 
have taught that the cerebrum is the organ which 
is responsible for the upbuilding of these new re- 
flexes. Want of space renders it impossible to 
NO. 2200, VOL. a2| 
Fru. t.—Mudspate-track opposite Veshab in the Zarafshan Valley. 
give an account of these experiments on the results 
of partial extirpation of the cerebrum, since these 
were given in such brief outline in the lecture that 
further abstraction is not possible. It is to be- 
hoped, however, that Prof. Pawlow will soon give 
to the world a book on the subject similar to his 
famous work on the ‘‘Work of the Digestive 
Glands,” since practically all the abundant litera- 
| ture on this new subject is only to be obtained in 
the Russian language at the present time. 
The next International Physiological Congress 
will be held in Paris in 1916, with Prof. Tigerstedt, 
of Helsingfors, as President. 
C. Lovatr Evans. 
THE DUAB OF TURKESTAN.* 
Eo its opening sentence this book raises an 
important question, of the propriety of appro- 
priating a word belonging to a language foreign 
to us and using it, 
in a sense equally foreign to 
From “ The Duab of Turkestan.” 
its native country, 
at variance with its original sense. 
in order to express a concept 
The word 
doab, signifying originally the confluence of two 
streams, and secondarily the tongue of land be- 
tween them, has been introduced by Prof. W. M. 
Davis for a portion of a coastal plain lying between 
two rivers which never unite, but flow independ- 
ently to the sea; in the form “‘duab” it is used 
by Mr. Rickmers for the country lying between 
two rivers, the Oxus and Jaxartes, which flow 
independently into the Sea of Aral, and includes 
not only the area of plain, which would come under” 
Prof. Davis’s use of the word doab, but the whole 
of the mountain region bounded on either side 
by the main streams of the two rivers. q 
1 “The Duab of | urkestan: 
some ‘l'ravels."" By W. Rickmer Rickmers. Pp. xv+564+plates+maps. 
(Cambridge: University Press, 1913.) Price 30s. net. 
A Physiographic Sketch and Account of § 
Ft tin 
