JUNE 21, 1901.] 
Here the facts actually known are duly set forth, 
and among other things it is shown that the 
rats were destroyed in great numbers, while it — 
seems doubtful whether the ‘ground-birds’ 
were actually exterminated in any instance. 
T. D. A. CoCKERELL. 
East Las Veeas, N. M., 
May 16. 1901. 
AN EARTHWORK DISCOVERED IN MICHIGAN. 
Mr. G. N. HAvuprMan, of Saginaw, Michigan, 
in a letter dated May, 1901, reports that ‘ there 
is on section 34, T. 21, N., R. 1 E., Ogemaw 
county, Mich., an earthwork [of horse-shoe 
shape]. The trench * * * is three feet’ deep, 
and in it stand forest trees. 
If any notice of this has ever been printed I 
should be glad to receive references to the same. 
I believe no note of this earthwork has pre- 
viously been made, although four earthworks 
in the same county are well known and are re- 
corded in the literature of archeology. 
HARLAN I. SMITH. 
PHYSIOLOGY IN THE SCHOOLS. 
TO THE EDITOR OF SCIENCE: The writer has 
a ‘horrible suspicion’ that T. Hough imputes 
the physiological questions, to which he demurs, 
tohim. Hedidnotpropound them. The high- 
school questions were taken from the text-book 
which the pupils had used, and if the text was 
legitimate, the questions were. 
It is the writer’s conviction that public school 
teachers are not generally qualified to teach 
physiology ; that physiology proper is too ab- 
struse for the grammar grades; and that the 
teacher in every grade should be expected to 
have a better knowledge of his subject than 
can be obtained from the elementary text placed 
in the hands of his pupils. Finally he may 
venture to express his fear that a little elemen- 
tary knowledge of the reasons for the non- 
increase in stature of the human skeleton 
throughout life might not be amiss to his 
learned critic even. 
S. W. WILLISTON. 
SHORTER ARTICLES. 
WHAT IS LIFE? 
Some thoughts, started by reading an article 
with the above title in Nature, Vol. 57, p. 188, 
SCIENCE. 
OE 
1898, by Horace Brown, and jotted down at 
that time, but laid aside, I have thought might 
perhaps interest the readers of SCIENCE, espe- 
cially as the subject continues to be agitated.* 
Heretofore in cases of dormant life, as in 
seeds kept for years, perhaps for centuries, or in 
dessicated infusoria, etc., in which under favor- 
able conditions active life is revived, it has 
been supposed that very slow metabolic changes 
still go on during the state of dormancy—life 
is supposed to be feeble, but not extinct. The 
same was supposed to be the case in seeds or 
bacteria exposed to intense cold of — 180° to 
— 200° C. by Pictet or even — 250° by Dewar. 
But it is now proved that at this temper- 
ature chemical affinity is destroyed and all 
chemical changes arrested, and therefore the 
chemical changes characteristic of life—metab- 
olism—also must cease. But with the return 
of heat they revive. Therefore, in this case, 
life seems to spring spontaneously from dead 
matter. Must we then revive the old doctrine 
of spontaneous generation? If not we must 
change or greatly modify our conceptions of 
life. 
From such experiments it is evident that, 
although life is, indeed, a distinct form of energy, 
yet its nearest alliance is with chemism. For 
as chemism is completely destroyed by extreme 
cold and again revived by heat, so life may be 
completely arrested by cold and again revived 
by heat—if the molecular structure characteristic 
of living protoplasm (whatever that may be) re- 
mains unchanged. 
What then is the necessary condition of life— 
or, to put it clearly, what is the difference 
between dead protoplasm and living protoplasm, 
or rather protoplasm capable of life? Evidently 
it is not a difference in chemical composition, 
for no change in this regard takes place in the 
act of death. It is, I suppose, a difference in 
molecular arrangement—a difference in allotropic 
condition. As the necessary condition of chemi- 
cal properties is a certain equivalent composi- 
tion : so the necessary condition of vital prop- 
erties is, in addition, a certain molecular con- 
stitution. But as equivalent composition may 
*Nature, Vol. 61, p. 67, 1899; Vol. 63, p. 420, 
1901. Revue Scientifique, Vol. 15, p. 201, 1901, and 
ScrENCE, Vol. 12, p. 774, 1900. 
