Licence: Public Domain Mark
Credit: A manual of veterinary physiology / by F. Smith. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
399/440 page 379
![the bladder and elongates the penis of the castrated animal, no doubt produces what Colin has recorded of stallions. The infl Lience of the cerebrum on the mechanism of erection, viz., in stimulating the centre in the cord and medulla, is well known. The first portion of the penis which receives the excess of blood in erection is the corpus cavernosum; the spongiosum and glans are not fully erect in the stalUon until the penis is introduced into the vagina; at the moment of ejacu- lation the glans swells enormously, apparently to cover or grasp the os uteri. The blood sent to the penis for the purpose of erection is practically imprisoned by the com- pression exercised by the muscles of the perinteum on the veins of the part, and this mechanism further maintains the blood pressure. If the nerves of the penis be divided in the horse, erec- tion is impossible, though desire may be intense. Gunther's and Colin's experiments have placed this beyond doubt. Though the organ in the horse assumes such considerable proportions, in the bull this is not so marked. The penis in this animal comes to a narrow point without any of the swelling observable in the stallion. In the ram, also, the penis is narrow and pointed, and the peculiar vermiform appendage at its extremity appears essential for successful impregnation, for if removed the animal proves sterile. Sexual Intercourse is of short duration in the majority of animals, excepting the dog and pig. Colin places it at 10 to 12 seconds for a vigorous stallion ; it is exceedingly rapid in the bull and ram, probably from the peculiar shape of their intromittent organ. The spermatic fluid is forced into the vagina, or even directly into the uterus ; the peculiar termination of the urethra of the horse, and the bulbous enlargement of the glans during the act of coition, would rather point to the fluid in this animal being directly passed, at any rate to some extent, into the os uteri, and the pointed ])enis of the bull and ram makes it nearly certain that much of the fecundating fluid passes directly into the uterus.](https://iiif.wellcomecollection.org/image/b21933480_0399.jp2/full/800%2C/0/default.jpg)
