APRIL 4, 1907 | 
NATURE 
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on 
Dr. Gordon has sought for a bacteriological test whereby 
particles shed from the skins may be detected in the air. 
He finds that a Staphylococcus (S. epidermidis albus of 
Welch, with certain attributes) is by far the most frequent 
organism of the skin, and another Staphylococcus of the 
scalp. Lastly, Dr. Alan Green records further experiments 
on chloroformed vaccine lymph and on the combined use 
of chloroform and glycerin in preparing lymph. The 
volume, therefore, contains much valuable matter, and is 
illustrated with a number of photographs. 
R. T. Hew ett. 
PULSATION IN ANIMALS.* 
ELLY-FISHES have been the subjects of frequent 
experimentation-—we need only refer to the admirable 
researches of Romanes—and Mr. Alfred G. Mayer, director 
of the Department of Marine Biology of the Carnegie 
Institution of Washington, has been able to draw some 
new and _ exceedingly interesting 
general conclusions from a study of 
their pulsations. When the marginal 
sense-organs of the jelly-fish Cassiopea 
are cut off, the disc is paralysed and 
does not pulsate in sea-water. If a 
ring-like cut, or a series of concentric 
broken-ring-like cuts, be made through 
the muscular tissue of the sub- 
umbrella, the mutilated dise (without 
marginal sense-organs) responds to a 
momentary stimulus, e.g. a mechanical 
or electrical shock, or a single touch 
‘with a crystal of potassium sulphate, 
and suddenly springs into unusually 
rapid rhythmical pulsation. This is 
regular and sustained like clockwork, 
and continues indefinitely in normal 
sea-water without further external 
stimulation. The waves of pulsation 
all arise from the stimulated point, 
and the labyrinth of sub-umbrellar 
tissue around this centre must form 
a closed circuit—the stimulus being 
transmitted by the diffuse nervous or 
epithelial elements of the  sub- 
umbrella. Any cut that breaks the 
circuit stops the waves of pulsation, 
and continuous movement cannot 
again be started. When each wave 
in a complete circuit returns to the 
centre it is réinforced and again sent 
out through the circuit. The centre 
once established remains a fixed point, 
while the disc continues to pulsate. 
The pulsation is fully twice as rapid 
as that of a normal Medusa, its rate 
varying with the length of the cir- 
cuit, and it is self-sustaining (i.e. sustained by internal 
stimuli) once it be started by an external momentary 
stimulus. 
Mr. Mayer has endeavoured by numerous experiments 
to discover the réle of the various salts in the sea-water, 
and he finds that the sodium chloride is the chief stimulant 
to pulsation in Cassiopea, while magnesium is the chief 
restrainer of pulsation, and counteracts the influence of 
the sodium chloride. Similarly, the heart of Salpa 
democratica, the heart of the embryo loggerhead turtle, 
and the branchial arms of the barnacle pulsate actively 
in solutions (e.g. Ringer’s) containing only common salt, 
potassium and calcium, magnesium being absent. Mag- 
nesium inhibits pulsation in all these cases. Thus the 
general réle of NaCl, K, and Ca in these cases is to com- 
bine to form a powerful stimulant producing an abnormally 
energetic pulsation, which, however, being exhausting, 
cannot continue indefinitely; and magnesium is necessary 
to control and reduce this stimulus, so that the pulsating 
Bm 
zy 
1“ Rhythmical Pulsation in Scyphomedusz.” 
By Alfred G. Mayer. 
Pp. 62; illustrated. 
(Washington : Carnegie Institution, rgo6.) 
NO. 1953, VOL. 75] 
Shapes cut from discs without marginal sense-organs. f 
The arrows indicate the paths of the waves of pulsation. 
organ is merely upon the threshold of stimulation. More 
concretely, the NaCl, K, and Ca of the sea-water unite 
in stimulating the pulsation of the jelly-fish, and in resist- 
ing the stupefying effect of the Mg, the general anesthetic 
effect of which has been well known since the researches 
of Tullberg in 1892. All four salts conjointly produce 
in sea-water an indifferent, or balanced, fluid which 
neither stimulates nor stupefies the disc (i.e. the 
medusa with marginal sense-organs excised), and _per- 
mits a recurring internal stimulus to produce rhythmic 
movement. 
Not only has the author shown us a new method of 
restoring pulsation in paralysed Medusz, but he has 
demonstrated that magnesium plays a most important réle 
in restraining, controlling, and thereby prolonging pulsa- 
tion in animal organisms. ‘‘ Rhythmical pulsation can be 
maintained only when a stimulus and an inhibitor counter- 
act one another, and cause the organism to be upon the 
threshold of stimulation; thus permitting weal internal 
stimuli to promote periodic contraction.’’ Thus, once 
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These will pulsate continuously in sea-water. 
more, marine biology justifies itself in contributing to the 
progress of general physiology. Vo Wale “Lic 
THE WEATHER AND THE CROPS. 
AN interesting paper on the correlation between the 
weather and the crops, by Mr. R. H. Hooker, head 
of the statistical branch of the*Board of Agriculture, was 
read before the Royal Statistical Society on January 15. 
The subject is very fully discussed by the method of 
correlation, partial coefficients of correlation being deter- 
mined between the produce of each crop and (1) the rain- 
fall, (2) the accumulated temperature above 42° F. during 
successive overlapping periods of eight weeks (first to eighth 
weeks of the year, fifth to twelfth, and so on). The crops 
dealt with include wheat, barley, oats, beans, peas, pota- 
toes, turnips and swedes, mangolds, hay from clover and 
rotation grass, and hay from permanent grass. As climatic 
conditions differ so materially in England and Scotland, 
and even in different parts of England, it was thought 
necessary to deal with a smaller area, and a group of eight 
