The experiments upon the pelvic viscera are not yet complete. The centers have been fairly well demonstrated, but the pathway of the nerve impulses concerned in the reflexes has not been determined. The following experiments were performed upon animals. The electrical stimulation of the rectum was followed by contraction of the muscles near the fourth lumbar vertebra and the lumbo-sacral articulation. Stimulation of the anus and urethra caused muscular contractions over the sacrum and along the tail. Sometimes, but not always, the leg muscles were also contracted. Stimulating manipulations of the tissues near the lumbo-sacral articulation were followed by imperfect movements of defecation, erection, or micturition. Artificial lesions involving the lower lumbar region caused dilatation of the arterioles of the rectum and bladder and the relaxation of the vesical and anal sphincters. In all the centers below the second lumbar vertebra the latent period was very much longer than in any other region subjected to experiment. In many of our first experiments we secured no effects whatever from this region. Probably these failures were due to too great haste in ceasing the observations. Stimulation of the ovaries and testes caused contraction of the muscles near the dorso-lumbar articulation. Stimulation of the Fallopian tubes, or the double uterus, did not cause perceptible muscular contractions in many instances, but in some animals the stimulation of these structures was followed by contractions of the muscles near the second lumbar vertebra. Stimulation of the uterine cervix caused contractions of the muscles near the lumbo-sacral articulation. Stimulation of the lining membranes of the body cavities caused more intense contractions than did the stimulation of their peritoneal coverings. Stimulating manipulations of the dorso-lumbar tissues caused vaso-constriction of the ovaries. The artificial lesion in this area caused dilation of the ovarian vessels, as well as the effects described in connection with the abdominal organs. Stimulating manipulations of the tissues near the second lumbar vertebra produced no perceptible effects upon the structures of the virgin or non-pregnant uterus in the time during which the observations were continued. The latent period is very long in the reactions involving the lumbar segments, and no other significance can be attributed to our failure in this series. Some of the animals subjected to experiment were found to be in various stages of pregnancy. The following observations were made upon them: As in virgin and non-pregnant animals, stimulation of the uterine cervix caused muscular contractions near the lumbo-sacral articulation. Stimulation of the body of the double uterus caused contraction of the muscles near the second lumbar vertebra. Uterine contractions were never initiated by the anesthesia, nor by manipulations of the uterus, nor by the slight electric currents used for the experiments. Stimulating manipulations near the second lumbar vertebra caused uterine contractions which were fairly regular, very strong, and continued until the death of the animal. These manipulations alone were accompanied by contraction of the uterine vessels and very great rigidity of the uterine cervix. Inhibition of the tissues near the lumbo-sacral articulation, or the maintenance of the artificial lesion in this region caused the dilatation of the cervical vessels and relaxation of the cervix. In a few instances, simultaneous stimulation of the tissues near the second lumber vertebra and inhibition of the tissues near the lumbo-sacral articulation was followed by partial delivery of the first foetus, though the period of pregnancy was not complete, and the animals had been subjected to considerable mutilations of the brain and thorax during a long period of anesthesia.
Multipolar cells from the lower triangle of the medulla. Method of Golgi. Objective 2-3 inch. |
