Abstract
In 1902 Fletcher 1 showed that the sartorius muscle of a frog will give a maximum contraction when stimulated every five minutes over a period of two hours in an atmosphere of pure nitrogen. In an atmosphere of oxygen, the same muscle will contract for a much longer time and the fatigue developing in an atmosphere of nitrogen may be removed by placing the muscle again in an atmosphere of oxygen.
If differentiated muscle has sufficient reserve energy to allow it to contract for a period without oxygen, the question arises, will not the same reserve be found in an actively growing tissue.
In a previous article in 1917 2 the author described a method which allows one to study quantitatively the effect of various concentrations of oxygen on the growth of cells in vitro. In that paper the main point studied was the relative effect of pure oxygen and various dilutions of oxygen in nitrogen on the rate and extent of the growth. The tissues used were fragments of heart muscle and other tissue of chick-embryo of various ages. These experiments showed that the growth was practically the same in an atmosphere containing 8 per cent. of oxygen as in one containing a much larger proportion of this gas or in a pure oxygen atmosphere.
A low concentration of oxygen beyond which no growth of cells will take place was also recorded. But as stated this was not accurately determined. There were certain discrepencies in the method of measurements and as must be stated here the tissues used for determining this point were fragments of the heart of 15, 16, and 18 day old chick-embryos.
In the present experiments, these objections to the technic used as outlined in the previous paper have been removed and tissues from embryos of various ages have been tested.
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