climatically similar to New Mexico, except that it is colder and has no rainy season in summer. Long, snowy winters and rains continuing well into the dry summer are the conditions which favor growth. The curve of the sequoia has been computed in the same way as that of the other trees. The period covered by the growth of the trees, however, is so great that the number of trees whose analyses are now available is not enough to give certainty to the corrections. Accordingly, after obtaining a curve corrected as accurately as possible both for age and longevity, I have tilted the whole line slightly in order to make the relative height at three or four fixed points correspond as nearly as may be with the height of the Caspian Sea at the same dates. This, however, has no effect upon the sinuosities of the curve, but merely upon the exact amount by which the earlier parts are higher than the later. Before we proceed to discuss the curve a word or two of explanation may be added. The horizontal lines indicate the growth in millimeters per decade. The extreme fluctuations of the early part of the curve give an exaggerated idea of the variability of the climate at that time. This is due to the small number of trees available. When more have been measured the extremely sharp character of the depressions and hollows, or of the arses and theses, as I have elsewhere called them, will disappear.

Examination of the curve shows that the climate of the interior of California has been subject to marked pulsations during the past 3,000 years. For instance, at the time of Christ the tree grew 30 per cent faster than at the end of the fifteenth century. Practically all the trees at the latter date were of large size with thoroughly developed root systems, and with a vast supply of strength stored up from the past. Moreover, they were growing high among the mountains where the supply of rain and snow was largest, and many of them were standing in swamps or beside brooks. If they could be so affected by drought as to show a decrease of 30 per cent in the amount of growth, other less favored plants must have suffered much worse. It is noticeable that in general the trees recover rapidly after a period of aridity and then fall off more slowly as another dry time approaches. This is important as an indication that climatic changes from dry to moist take place rapidly, while those in the reverse direction are slow. It bears also on another point. It may be suggested that the inequalities in the curve are due to accidents such as fires. In the first place, this is not probable, since the 451 trees were located in four different areas with a distance of 60 miles between the extremes and with high mountains and deep valleys intervening. The rapid rise and gradual fall of the curves, however, disproves any such supposition. An accident, such as a fire or anything else, would suddenly cause the trees to grow slowly, after which they would gradually recover, whereas the actual case is the reverse of this.

at the time of Christ, for example, or those which center 1000 or 1600 A. D. The agreement is so close that it can scarcely be a matter of chance. Further discussion of the subject must be deferred for the present. We can here merely sum up the main conclusions. The study of the trees of New Mexico and California in the first place seems to confirm the conclusions derived from the ruins and physiographic evidences found in the drier parts of North America. It thus shows that the methods upon which those conclusions are based are sound, and that the results derived from such methods whether in America or Asia are valid. In the second place, the trees confirm the theory of pulsatory climatic changes. They apparently show that the climate of the earth is subject to pulsations having a period of centuries. In the third place, the rate of growth of the trees indicates that in the distant historic past the moist epochs were on the whole moister than the similar epochs in more recent times. Fourth and last, we are led to conclude that the main climatic changes of America are synchronous with those of Asia and are of the same kind. This does not mean that changes in tropical countries are like those in the Temperate Zone. It does indicate, however, that in the temperate continental regions of the world, in both the eastern and western hemispheres, periods of exceptional aridity or of exceptional moisture have occurred at approximately the same time, and have sometimes lasted for centuries. Hitherto this point has been open to question, and therefore historians and other students of man have been skeptical as to the possibility that climatic changes could have been of sufficient importance profoundly to influence history. With the fuller application of the methods here discussed, we shall soon be able to determine the exact nature and degree of climatic changes throughout historic time, and then we shall have the basis for a true appreciation of their effect upon history.

THE SURVIVAL OF ORGANS AND THE "CULTURE" OF

LIVING TISSUES.1

By R. LEGENDre,

Preparator of Zoology, National Museum of Natural History, Paris.

[With 4 plates.]

The Nobel prize in medicine for 1912 has just been awarded to Dr. Alexis Carrel, a Frenchman, of Lyon, now employed at the Rockefeller Institute of New York, for his entire work relating to the suture of vessels and the transplantation of organs.

The remarkable results obtained in these fields by various experimenters, of whom Carrel is most widely known, and also the wonderful applications made of them by certain surgeons have already been published in La Nature (No. 1966, Jan. 28, 1911).

We will not repeat what has been said concerning these researches, but we will take the occasion of the awarding of the Nobel prize to mention other biological studies in which Dr. Carrel has been engaged.

The journals have frequently spoken lately of "cultures" of tissues detached from the organism to which they belonged; and some of them, exaggerating the results already obtained, have stated that it is now possible to make living tissues grow and increase when so detached.

Having given these subjects much study I wish to state here what has already been done and what we may hope to accomplish. As a matter of fact we do not yet know how to construct living cells; the forms obtained with mineral substances by Errera, Stephane Leduc, and others, have only a remote resemblance to those of life; neither do we know how to prevent death; but yet it is interesting to know that it is possible to prolong for some time the life of organs, tissues, and cells after they have been removed from the organism.

The idea of preserving the life of greater or lesser parts of an organism occurred at about the same time to a number of persons,

Translated by permission from La Nature, Paris, No. 2058, Nov. 2, 1912.

and though the ends in view have been quite different the investigations have led to essentially similar results. The surgeons, who for a long time have transplanted various organs and grafted different tissues, bits of skin among others, have sought to prolong the period during which the grafts may be preserved alive from the time they are taken from the parent individual until they are implanted either

FIG. 1.-The apparatus of Kronecker for the study

of the heart of the frog when removed from the

upon the same subject or upon another. The physiologists have attempted to isolate certain organs and preserve them alive for some time in order to simplify their experiments by suppressing the complex action of the nervous system and of glands which often render difficult a proper interpretation of the experiments. The cytologists have tried to preserve cells alive outside the organism in more simple and well defined conditions. These various efforts have already given, as we shall see, very excellent results both as regards the theoretical knowledge of vital phenomena and for the practice of surgery.

It has been possible to preserve for more or less time many organs in a living condition when detached from the organism. The organ first tried and which has been most frequently and completely investigated is the heart. This is because of its resistance to any arrest of the circulation and also because its survival is easily shown by its contractility. In man the heart has been seen to beat spontaneously and completely 25 minutes after a legal decapitation (Renard and Loye, 1887), and by massage of the organ its beating may be restored after it has been arrested for 40 minutes (Rehn, 1909). The heart of the dog has been known to beat 96 hours after death, that of the tortoise for 8 days, and Burrows (1911) observed the heart of an embryo chick to beat for 3 days after its removal. By irrigation of the heart and especially of its coronary vessels the period of survival may be much prolonged.

animal. b, c, Tubes containing defibrinated blood; h, cock for distribution of the same;

r, cup containing the isolated heart fixed upon the end of a two-way canula; ha, cock upon an overflow tube communicating with a float manometer.