704 



SCIENCE 



[N. S. Vol. XLI. No. 1063 



Growth and Death" and made them the 

 basis of a book published the foUowiag 

 year. For him, the subject meant cell meta- 

 morphosis, with which he had been familiar 

 through all his studies in histology and 

 embryology, but what he sought in this sub- 

 ject of "Age, Growth and Death" was a 

 scientific solution of the problem of old age 

 which should have — I quote his words — 

 "in our minds, the character of a safe, 

 sound and trustworthy biological conclu- 

 sion." He ventured to think that some 

 contemporary students of the phenomena of 

 longevity had failed to exercise sufficient 

 caution in forming their conclusions. 

 Nevertheless, Minot was a scientific opti- 

 mist; full of hope for perpetual progress 

 and for useful results at many stages of the 

 long way. These characteristics appeared 

 clearly in the following passage, taken from 

 the first lecture of that course at the Lowell 

 Institute : 



I hope before I finish to eonvince you that we 

 are already able to establish certain significant 

 generalizations as to what is essential in the 

 change from youth to old age, and that in conse- 

 quence of these generalizations now possible to us 

 new problems present themselves to our minds, 

 which we hope really to be able to solve, and that 

 in the solving of them we shall gain a sort of 

 knowledge which is likely to be not only highly 

 interesting to the scientific biologist, but also to 

 prove in the end of great practical value. 



There spoke the cautious, modest, hope- 

 ful scientist, expectant of good. Such is 

 the faith which inspires the devoted lives of 

 scientific inquirers. 



Charles W. Eliot 



TEE STIMULATION OF GBOWTH^ 

 I 

 The growth of living organisms differs 

 from that of crystals in three essential fea- 

 tures. While the crystal grows only in a 

 supersaturated solution of its own sub- 

 1 Eead at the meeting of the National Academy 

 in Washington, April 19, 1915. 



stance, living organisms can grow inde- 

 finitely in even a very low concentration 

 of their nutritive solution ; second, the nu- 

 tritive solution need not and perhaps should 

 not contain the compounds found in the 

 cells, but only their split products, while in 

 the ease of the crystal the substance of 

 crystal and solute must be identical. And 

 thirdly, growth leads in living cells to the 

 process of cell division as soon as the mass 

 of the cell reaches a certain limit. Need- 

 less to say this process of cell division can 

 not even metaphorically be claimed to exist 

 in a crystal. 



The fact that the cell can grow in a very 

 low concentration of its nutritive solution, 

 and the further fact that the nutritive solu- 

 tion only needs to contain the building 

 stones for the complicated compounds of 

 the cell, find their explanation in the as- 

 sumption of the existence of synthetic 

 enzymes or synthetic mechanisms in the 

 cell. 



The problem of growth is linked with 

 that of death and immortality, since it 

 would follow from our definition that the 

 growth of a cell should go on eternally in a 

 proper nutritive solution and under suita- 

 ble conditions of temperature, provided 

 that the synthetic catalyzers last and that 

 they synthetize their own substance.^ This 

 is apparently true for bacteria and perhaps 

 also for protozoa. Weismann has claimed 

 inomortality for all unicellular organisms 

 and for the sex cells of metazoa, while he 

 concedes mortality to the body cells. Leo 

 Loeb recognized that immortality may be 

 claimed also for the cells of malignant 

 tumors, like cancer, for he had found that 

 when he transplanted cancer cells on other 

 animals the cells of the original cancer and 



2 This latter assumption leads to the coimection 

 of the problem of growth with that of autocataly- 

 sis as suggested first by the writer in 1906 and 

 worked out subsequently in the papers of Wo. 

 Ostwald and T. B. Eobertson. 



