Jacques Loeb

“ The idea that the body cells are naturally immortal and die only if exposed to extreme injuries such as prolonged lack of oxygen or too high a temperature helps to make one problem more intelligible. The medical student, who for the first time realizes that life depends upon that one organ, the heart, doing its duty incessantly for the seventy years or so allotted to man, is amazed at the precariousness of our existence. It seems indeed uncanny that so delicate a mechanism should func­tion so regularly for so many years. ”

“ We know that every living being is able to transform food-stuffs into living matter; and we also know that not only the compounds which are formed in the animal body can be produced artificially, but that chemical reactions which take place in living organisms can also be repeated at the same rate and temperature in the laboratory. ”

“ It is this positive helio­tropism which makes them move upward where they find their food, when the mild air of the spring calls them forth from their nest. At the top of the branch, they come in contact with a leaf, and chemical or tactile influences set the mandibles of the young caterpillar into activity. If we put these larvæ into closed test-tubes which lie with their longitudinal axes at right angles to the window, they will all migrate to the window end, where they stay and starve, even if their favourite leaves are close behind them. They are slaves of the light. ”

“ It is, therefore, no exaggeration to state that the number of species existing to-day is only an infinitely small fraction of those which can and possibly occasionally do originate, but which escape our notice because they can not live and reproduce. Only that limited fraction of species can exist which possesses no coarse disharmonies in its automatic mechanism of preservation and reproduction. Disharmonies and faulty attempts in nature are the rule, the harmonically developed systems the rare exception. ”

“ When, however, the biologist is confronted with the fact that in the organism the parts are so adapted to each other as to give rise to a harmonious whole; and that the organisms are endowed with structures and instincts calculated to prolong their life and perpetuate their race, doubts as to the adequacy of a purely physico­chemical viewpoint in biology may arise. The difficulties besetting the biologist in this problem have been rather increased than diminished by the discovery of Mendelian heredity, according to which each character is transmitted independently of any other character. ”

“ In many insects and in man the cells of the female have two sex-chromosomes. In a certain stage of the history of the egg one half of the chromosomes leaves the egg (in the form of the "polar-body") and the egg keeps only half the number of chromosomes. Each egg, therefore, retains only one X or sex-chromosome. In the male the cells have from the beginning only one X-chromosome and each primordial spermatozoon divides into two new (in reality into two pairs of) spermatozoa, one of which contains an X-chromosome while the other is without such a chromosome. ”

“ The reason that an egg once fertilized with sperm cannot be fertilized again may be found in a group of facts which we will now discuss, namely, the self-sterility of many hermaph­ro­dites. The fact that hermaph­ro­dites are often self-sterile, while their eggs can be fertilized with sperm from a different individual of the same species has played a great rôle in the theories of evolu­tion. We are here only concerned with the mechanism which determines the block to the entrance of a spermato­zoön into an egg of the same hermaph­ro­ditic individual. ”

“ Our wishes and hopes, disappointments and sufferings have their source in instincts which are comparable to the light instinct of the heliotropic animals. The need of and the struggle for food, the sexual instinct with its poetry and its chain of consequences, the maternal instincts with the felicity and the suffering caused by them, the instinct of workmanship and some other instincts are the roots from which our inner life develops. ”

“ By inheritance the mass of enzymes is approximately the same and in this way all the embryos beat at the same rate (within the limits of the fluctuating varia­tion) at the same temperature. This identity exists, however, only as long as the embryo is relatively quiet in the egg. As soon as the embryo begins to move this equality disappears since the motion influences the heart-beat and the motility of different embryos differs.
In man the number of disturbing factors is so great that no equality of the rate for the same temperature can be expected. ”

“ The specific substances which accelerate the oxidations at body temperature sufficiently to allow the maintenance of life are the so-called ferments of oxidation.
The work of Lavoisier and Laplace not only marks the beginning of scientific biology, it also touches the core of the problem of life; for it seems that oxidations form a part, if not the basis, of all life phenomena in higher organisms. ”

“ The work on Mendelian heredity has shown that an extremely large number of independently transmissible Mendelian factors help to shape the individual. It is not yet proven that the organism is nothing but a mosaic of Mendelian factors, but no writer can be blamed for considering such a possibility. If we assume that the organism is nothing but a mosaic of Mendelian characters it is difficult indeed to understand how they can force each other into a harmonious whole6; even if we make ample allowance for the law of chance and the corresponding wastefulness in the world of the living. ”

“ Scientifically, however, individual life begins (in the case of the sea-urchin and possibly in general) with the acceleration of the rate of oxidation in the egg, and this acceleration begins after the destruction of its cortical layer. Life of warm blooded animals—man included—ends with the cessation of oxidation in the body. As soon as oxidations have ceased for some time the surface films of the cells, if they contain enough water and if the temperature is sufficiently high, become permeable for bacteria, and the body is destroyed by microorganisms. ”

“ It is quite possible that the apparent immunity to a transplanta­tion of cancer produced by Jensen, Leo Loeb, and Ehrlich and Apolant through the previous transplanta­tion of tissue in such an animal was due to the fact that this previous tissue transplanta­tion led to an increase in the number of lymphocytes in the animal. The medical side, however, lies outside of our discussion, and we must satisfy ourselves with only a passing notice. The facts show that each warm-blooded animal seems to possess a specificity whereby its lymphocytes destroy transplanted tissue taken from a foreign species. ”

“ It is seemingly often taken for granted by laymen that "truth" in biology or science in general is of the same order as "truth" in certain of the mental sciences; that is to say, that everything rests on argument or rhetoric and that what is regarded as true to-day may be expected with some probability to be considered untrue to-morrow. It happens in science, especially in the descriptive sciences like paleontology or zoology, that hypotheses are forwarded, discussed and then abandoned. ”

“ And yet we are better off in regard to our knowledge of the instincts than we are in regard to morphogenesis, as in the former we can show that the apparent instincts in some cases obey simple physico­chemical laws with almost mathematical accuracy. Since the validity of the law of gravita­tion has been proved for the solar system the idea of design in the motion of the planets has lost its usefulness, and this fact must serve us as a guide wherever we attempt to put science beyond the possibility of mysticism. ”