The mechanistic conceptions of life : biological essays / by Jacques Loeb.

  • Jacques Loeb
Date:
1912
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Licence: In copyright

Credit: The mechanistic conceptions of life : biological essays / by Jacques Loeb. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    these experiments the action of the spermatozoon upon the egg was very incompletely imitated. When a spermatozoon enters into the egg it causes primarily a change in the surface of the egg which results in the formation of the so-called membrane of fertilization. This phenomenon of membrane formation which had always been considered as a phenomenon of minor importance did not occur in my original method of treating the egg with hypertonic sea-water. Six years ago while experimenting on the Californian sea-urchin, Strongylo- centrotus purpuratus, I succeeded in finding a method of causing the unfertilized egg to form a membrane without injuring the egg. This method consists in treating the eggs for from one to two minutes with sea-water to which a definite amount of butyric acid (or some other monobasic fatty acid) has been added. If after that time the eggs are brought back into normal sea-water, all form a fertilization membrane in exactly the same way as if a spermatozoon had entered. This membrane formation or rather the modification of the surface of the egg which underlies the membrane formation starts the development. It does not allow it, however, to proceed very far at room temperature. In order to allow the development to go farther it is necessary to submit the eggs after the butyric acid treatment to a second operation. Here we have a choice between two methods. We can either put the eggs for about one half-hour into a hypertonic solution (which contains free oxygen); or we can put them for about three hours into sea-water deprived of oxygen. If the eggs are then returned to normal sea-water containing oxygen they all develop; and in a large number the development is as normal as if a spermatozoon had entered. The essential feature is therefore the fact that the develop- ment is caused by two different treatments of the egg; and that of these the treatment resulting in the formation of the membrane is the more important one. This is proved
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