_ common sense. 

APRIL 28, 1923] 
NATURE 
57! 

Mr. O'Hea must, however, have more facts which 
enable him to deny the use of an insect’s eyes for 
vision in the face of all the work of Lord Avebury, 
Plateau, Forel, and many others. 
As for Arachnida, an immense number of examples 
could be quoted as indicating power of vision. The 
following are obvious (and are cases where “ convec- 
tion currents "’ are definitely excluded) : 
' A male Attid will start to dance before the female, 
though a glass partition separate them, and he turns 
his head to watch her as she moves. 
I have at present two specimens of Lycosa Narbon- 
ensis, which, when out of their burrows, will dart back 
when a sudden movement is made near them} that 
is within about three yards. (They are always under 
glass, so that convection currents will explain nothing.) 
A slow approach, as with the fly, does not disturb them. 
It seems to me that, in testing,Commander Hilton 
Young’s hypothesis, we cannot assume the absence of 
insect vision on such slender evidence as that brought 
forward by Mr. O’Hea. We must either experiment 
_ with species which are known to possess absolutely no 
power of sight, or obliterate the eyes with a varnish, 
and then see how the insect behaves in the neighbour- 
hood of a solid body. G, H. Locket. 
Salmon’s Cross, Reigate, Surrey, 
April 15. 

Science and Economics. 
Pror. Soppy is an eminent chemist and physicist, 
and it is consistent with his own investigations that 
he should seek for the ‘‘ natural fundamental basis 
of the economic system under which we perish ”’ 
(Nature, April 14, p. 497). If the natural basis of 
the system be such as to cause us to perish, the object 
of a re-examination is, perhaps, to alter Nature and 
reconstruct de novo. r, does Prof. Soddy mean 
that there are natural economic laws of which we 
__ are, as yet, not aware, and for which we should search ? 
We know, however, that nineteenth-century econo- 
mists enunciated natural laws of economics such as 
competition (survival of the fit) and supply and 
demand (action and reaction). These laws, neverthe- 
less, were not “‘ natural’’ to economics; they were 
adapted from Nature, as then expounded, and applied 
artificially by the governments in certain countries. 
Prof. Soddy now says, and with some reason, that 
the present economic system is an offence against 
It seems then that the natural 
obvious truths of the nineteenth century as inter- 
preted economically are, in this century, both un- 
scientific and senseless. Many no doubt will agree 
with him that the complex modern financial system 
which evolved through several centuries pari passu 
with science, and admirably served to stimulate, 
restrain, and direct the desires and ambitions of an 
imperfect human race, does not function as re- 
sponsively as it did. Age may be the cause; it has 
not renewed itself by new forms of thought as has 
science. But, whatever the cause, one ventures to 
disagree with Prof. Soddy when he says that no 
one pretends to understand the system. This is 
true only as one might say ‘‘no one pretends to 
understand the ‘atomic’ theory ’’: a few do—that 
is, those who conduct the operations. Certain 
axioms hold good until new conditions are intro- 
duced ; but it is somewhat easier, one would think, 
to find the formule necessary to control operations 
under new conditions in a laboratory than in the 
world of human affairs. In the former, mathematics 
are at hand, but of what assistance are these scientific 
methods in dealing with complex and unequally 
developed human beings whose conflicting desires 
and opinions cannot be mathematically computed 
and resolved by formule ? 
NO. 2791, VOL. 111] 
Again, Prof. Soddy’s assertion that the production 
of wealth is now ‘‘a relatively finished science ’’ has a 
ring of finality hitherto unassociated with science. 
Many civilisations have shown evidences of great 
wealth, and its production is always a finished science 
at any time in an epoch, though relatively so to another. 
In our own day the need for human labour has not 
yet been entirely eliminated. It is even less probable 
that the distribution of wealth will ever become a 
finished science—at least, until ‘‘ Earth's last picture 
is painted.’ Were the dispensers of credit (whether 
by patronage or ‘‘ democratic control ’’) to achieve 
a temporary perfection in adjusting the desires and 
deserts of the social hierarchy even in regard to 
material things, the mere force of individuality in 
human beings would upset the balance in time, and 
the fact of evolution makes this event inevitable, 
as history shows. There may be a science of the 
distribution of wealth, and, if so, it is probably 
associated with the science of government, an art in 
which rulers and princes of earlier times were especially 
trained ; but one must conclude that its principles 
are not those of applied physics, for mankind cannot 
be controlled, transmuted, and led so rapidly and 
readily on the path of evolution as can the ‘‘ elements” 
in the physicist’s laboratory. 
The ultimate basis of credit in any age is character 
and ability, on which have been founded the Codes 
of Laws and social formule of all great civilisations 
from the earliest Laws of Manu. It may be as well, 
therefore, for the preservation of our modern know- 
ledge, that the system by which “ tokens of wealth ” 
are distributed should not be radically changed until 
character is once more clearly defined and appreciated 
by all classes. W. WILSON LEISENRING. 
Oakley House, Bloomsbury Street, 
London, W.C.1, April 16. 


Effect of Plant Extracts on Blood Sugar. 
(By CaBLe.) 
In the early days of my investigations in connexion 
with insulin, I predicted that whenever glycogen 
occurred in Nature an insulin-like substance would 
also be found. Putting this theory to the test, I 
obtained positive results first with clam tissue, and 
later with yeast. This result was obtained during 
the latter part of January. In the light of this latter 
result, my mode of reasoning was changed. If yeast 
contains an insulin-like hormone, other plants may 
also contain it. Extracts of tissue of a variety of the 
higher plants were, therefore, prepared, and the effect 
of subcutaneous injection of these extracts upon the 
blood sugar of the normal rabbit was ascertained. 
The effect of certain plant extracts upon the blood 
sugar of depancreated dogs was also studied. Ex- 
tracts made from onion tops, onion roots, barley 
roots and sprouted grain, green wheat leaves, bean 
tops, and lettuce were found to produce marked 
hyperglycemia in normal rabbits. The day following 
the administration of an extract of green onion tops 
to a depancreated dog with a blood sugar of o:190 
per cent., a blood sugar of o-ogo per cent. was ob- 
served. The results of this investigation were com- 
municated to the Society for Experimental Biology 
and Medicine at the meeting in New York City on 
March 21, when I suggested the name “‘ Glucokinin ” 
for this new plant hormone. Since that date I notice 
in Nature of March Io a letter by Messrs. Winter 
and Smith stating that they have obtained positive 
results with yeast extracts. These authors would, 
therefore, share coincident priority with me in this 
particular. J. B. Coxxip. 
Biochemical Laboratory, University of Alberta, 
April 21, 
