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"Let the states of equilibrium and harmony exist in perfection and a happy order will prevail through heaven and earth and all things will be nourrished and flourish. " (MENCIUS, in "The Doctrine of the Mean". ) In their natural environment the various plants and animals that have inhabited a region for ages have found a natural balance. The population of plants and animals of such a region appears to regulate itself auto matically; the number of each species is kept within rather strict limits by a natural balance of forces. The introduction of a new element in such an equilibrated situation may result in a "disaster" when the balance of forces that acted as a perfect self-steering device up till the introduction of that new element, fails to keep the number of that element under control. A well known example for this type of (man's) "interference with nature's balance of forces" is the importation of rabbits in Australia. Because Australia's fauna did not include any of the rabbit's "natural enemies" a "rabbit population explosion" followed this unhappy decision. An equilibrated situation can become disturbed in a different way. An example of another type of (man's) "interference with nature's balance of forces" is the introduction of modern technology and medicine in up till recently "backward" countries. The ensuing raise in available food and the better hygienic standards removed the older checks on population increase such as famine and peri-natal death.
Sommario
I. Introduction.- II. Pituitary tumours in mice and rats.- A. A survey of the literature.- B. 1. Discussion.- III. The incidence and the rate of growth of experimental pituitary tumours in various strains of mice and in rats.- A. Experimental.- B. Discussion and conclusion.- IV. Morphological characteristics of experimental pituitary tumours of mice of different inbred strains.- A. Comparison of the morphology of oestrone-induced and "radiothyroidectomy"-induced pituitary tumours employing a tri-chrome stain.- B. Differentiation of the two types of pituitary tumours by the PAS reaction.- V. The thyroid stimulating hormone (TSH) content of experimentally induced pituitary tumours in mice.- A. Substances in mouse pituitary homogenates interfering with a comparative TSH-assay.- B. Comparative assays of the TSH content of pituitaries of mice treated in various ways to induce pituitary tumour development.- VI. General Summary.- References.
