666 
stimulation, Anzemia of the stomach experimentally produced 
by blocking the thoracic aorta cuts short the normal contrac- 
tions of the organ. The cerebral centres for the gastric move- 
ments and tone, which have been described by many observers, 
notably by Bechterew and Opendowsky, were not found, 
although diligently searched for. No definite result upon the 
movements of the stomach seemed to result from any cerebral 
stimulation. 
Prof. Schafer contributed a communication on the diuretic 
action of pituitary extracts, based on recent researches by 
Dr. Magnus, of Heidelberg, and himself. He showed a series 
of tracings exhibiting by the graphic method the effect that 
intravenous injection of extract of pituitary body has upon the 
activity of the kidneys. The epithelial part of the pituitary 
body yields an extract which causes a marked increase in urinary 
secretion. This part of the gland had always previously been 
supposed inert. The diuretic action now proven to be exerted 
by.the gland had, Prof. Schafer urged, a direct bearing upon the 
disease called acromegaly, in which the pituitary body was 
enlarged and diuresis was present. 
Prof. Gotch brought forward an experiment upon fatigue and 
nerve. It had long been held that repeated or excessive activity 
caused fatigue of nerve-endings, but had no effect upon the fibres 
which conduct the nervous impulses. Herzen had recently 
questioned the truth of the above generally adopted view. 
Herzen stated that after a nerve-trunk had been subjected to 
repeated stimuli, the subsequent response of the nerve shows 
signs of impairment when examined by electrical tests. This 
impairment it had been the object of the present obsery- 
ations to examine, and they showed that the impairment 
was a change which was confined in its situation to the neigh- 
bourhood of the place of the electrodes by which the electric 
currents used for fatiguing the nerve were‘applied to the nerve. 
Were the effect a true fatigue effect, its locus should not be con- 
fined to the electrode region, but should be distributed throughout 
the nerve, because the process of conduction of nerve-impulses 
occupying the whole length of the nerve, the true fatigue which 
arose as their after effect must have a similar distribution. The 
changes which were confined to the immediate neighbourhood 
of the electrodes by which the long series of “ fatigue ”-pro- 
ducing currents were introduced were those to which much 
attention has long been devoted as electrotome. Probably the 
process involved was one of electrolysis, and certainly its relation 
to fatigue in the true sense was at most extremely remote. For 
the experiments the capillary electrometer had been employed ; 
the electric differences studied had been given by the nervous 
impulse in response to a single induction current. 
Dr. Edridge-Green brought forward evidence regarding the 
distribution in the retina of the photo-sensitive pigment, the 
visual purple. This pigment belongs to the ‘ rods” only, and 
is not present inthe ‘‘cones.” Nevertheless, Dr. Edridge- 
Green finds that it is present in the central region of the retina, 
a region in which there are cones only and no rods. On 
examining the retina of the monkey, when that animal had, in 
order to increase the amount of visual purple, been kept in the 
dark for twenty-four hours, the central region of vision, the 
yellow spot, instead of being free from visual purple was the 
most purple part of the whole retina. The purple was, how- 
ever, seen by microscopic examination to be around and not 
actually in the cones. He advanced the theory that the 
cones were only sensitive to changes in the visual purple, not to 
light itself. 
Dr. Osborne communicated the results of researches on 
glycogen carried out in conjunction with Dr. Zobel. Glycogen 
when hydrolysed by a diastatic ferment gives rise to bodies very 
similar to those derived from starch. Amongst these is the so- 
called isomaltose, shown by Brown and Morris to be a mixture 
of maltose and a dextrin-like body. When acted on by saliva, 
glycogen gives dextrins, dextrose and maltose. 
Dr. C. S. Myers referred to observations on the smallest 
perceptible musical tone-difference as examined in the people of 
Scotland and of the Torres Straits. The investigations had been 
conducted by means of tuning-forks. The least perceptible 
tone-difference among the children of Murray Island was not 
widely different from those of the children of Aberdeenshire. 
But with practice the Aberdeenshire children improved more 
readily and uniformly. The adult Murray Islanders for the 
most part failed to detect a semi-tone interval. The average 
difference of vibration-frequency just distinguishable by the 
NO. 1722, VOL. 66] 
NATURE 
[OcToBER 30, 1902 
Adult Murray Islanders was fifteen vibrations per second, 
whereas for the adult Scotch examined it was nine vibrations. 
Dr. Page May gave an excellent demonstration of sections of 
the brain and of the spinal cord of the camel. 
Mr. Barcroft described work dealing with a series of observ- 
ations on the quantitative estimation of urea. 
MAGNETIC WORK OF THE UNITED STATES 
COAST AND GEODETIC SURVEY, OUT- 
LINED FOR JULY 1, 1902—/JUNE 30, 1903. 
(2) [AND Magnetic Survey Work.—The determination of the 
three magnetic elements at 400-500 stations distributed 
principally in Virginia, New Jersey, Pennsylvania, Ohio, 
Michigan, Kansas, Nebraska, Texas, Arkansas and Florida. 
(6) Magnetic Observatory Work.—The continuous operation 
of the four magnetic observatories situated at Cheltenham, 
Maryland; Baldwin, Kansas; Sitka, Alaska ; and near Hono- 
lulu, Hawaiian Islands ; also the selection of sites and prepara- 
tions of plans of an observatory in Porto Rico or vicinity, and 
another in the extreme western part of the United States. [The 
International Committee on Terrestrial Magnetism and Atmo- 
spheric Electricity at the Bristol Conference in 1897 recom- 
mended Porto Rico as a suitable and favourable site. The 
recent magnetic disturbances experienced simultaneously with 
volcanic eruptions in Martinique will now make the vicinity of 
Porto Rico an especially important location for a fully equipped 
magnetic observatory. } 
(c) Ocean Magnetic Survey Work.—The inauguration of 
magnetic work on board ship in connection with regular trips 
of vessels engaged in coast survey work. [In this connection 
it is also proposed during the coming winter to make some trial 
investigations of the distribution of the magnetic elements over 
the frozen portions of Lakes Michigan, Superior and Huron in 
the vicinity of the Straits of Mackinac. The necessary observ- 
ations at shore stations and on islands will be made in the fall and 
spring. ] 
_ (ad) Special znvestigations conducted at the magnetic observ- 
atories and at certain educational institutions by persons available 
as ‘‘ associate magnetic observers.” 
(e) Ad the office at Washington a special effort will be made 
to bring all computations of field work performed and investiga- 
tions conducted since July 1, 1899, up to date and prepare 
results for publication. 
THE “SUDD” OF THE WHITE NILE: 
A RECENT number of the Geographical Journal contains a 
paper on the ‘‘sudd” of the White Nile, by Dr, Edward S. 
Crispin, explaining the method of opening up the true river bed 
employed by Major Matthews, who commanded the Sudd 
Expedition of 1901-1902. The first difficulty is to find the 
position of the river bed; this is done by probing, the depth 
suddenly increasing to 15 or 20 feet. Next the top growth, con- 
sisting mostly of papyrus, is cut down or burnt ; and it was noted 
that when the papyrus was fired the fire frequently spread along 
what was afterwards found to be the true bed of the river. Men 
are then landed on the cleared surface and the sudd cut along 
the river banks with saws; next transverse cuts are made, 
dividing the sudd into blocks of size convenient for the steamer 
to tear out. The bows of the steamer are run into the block, 
and the loop of a steel hawser, both ends of which are made 
fast to the steamer, is passed over the bows and trodden into a 
trench cut on the surface of the block. The steamer then goes 
full speed astern, men standing on the hawser to keep it in 
position, and after a number of trials the block is torn away. 
The block is then towed clear and cast adrift to float down 
stream, when it is gradually disintegrated. We reproduce figures 
illustrating (2) the steamer towing out a block of sudd, showing 
the men standing round and holding the hawser in position, and 
(4) the block let go in open water and floating down stream. 
The chief growths in the sudd are papyrus and tiger or 
elephant grass, a kind of bamboo growing to a height of 20 
feet or more. Up these climbs a creeper of the convolvulus 
species. There is also abundance of ambatch and a long 
