the Action of Glandular Extracts upon the Contractions of the Uterus

The uterine tissue consists of unstriped muscle fibre and ganglia of the sympathetic system imbedded in it. The sacral roots and pelvic nerve do not enter into the composition of the uterine plexus. In the rabbit, irritation of the hypogastric nerve produces vasoconstriction and contraction of the uterus. In cats, stimulation of the hypogastric nerve produces at one time contraction and at other times relaxation of the uterus. Dixon2 has shown that ergotoxin paralyzes the augmentor fibers and leaves the inhibitory fibers in the sympathetic intact. In the rabbit's uterus the augmentor fibers, always predominate; hence an irritation always produces a rise of tonus in the uterus. After paralyzing the augmentor fibers with ergotoxin, adrenalin excites the inhibitory fibers and relaxes the uterus. In the unimpregnated uterus of the cat adrenalin relaxes the uterus, but with a pregnant uterus it causes contraction. However, Fardon a found that when nicotin is given first a contraction of the nonpregnant uterus is caused by adrenalin instead of the usual relaxation. Adrenalin is supposed to act on nerve endings; hence nicotin must act on these nerve terminals or on the muscle itself. This reversal of action of adrenalin by previous use of nicotin is not due to a paralysis of the inhibitory nerve endings, for if ergotoxin be added after the reversal has been produced, the action of adrenalin is once more reversed and produces inhibition.