Abstract
In a search for the mechanism of the action of choline esters, it was desired to find the earliest stage at which a choline ester produces constriction in the iris, and to follow the rate of change, if any, in the amount of constriction as the iris develops. It was also desired to find what relation this action has to the development of the muscle and of the innervation.
For the study here reported, embryo pigs were obtained at the packing house at the time of removal from the dead mother, still at approximately body temperature. Some of them were kept at body temperature, some allowed to cool at room temperature, and others were placed in Locke or other physiological solution at 0°C. Carbaminoyl choline chloride solution was placed on the cornea of the right eye and the left eye was used as a control. Sometimes the eyes were left in the head but usually they were excised and placed in glass cups. The amount of constriction produced was determined by measuring the diameter of the pupil with a pair of fine dividers and a millimeter scale and comparing it with the diameter of the control pupil.
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