The canal of the urethra runs in the corpus spongiosum. Each of these three corpora is firmly united to the pubic bone behind.
They are constructed of an outer sheath from the inner surface of which numerous fine membranous partitions stretch, dividing the whole up into numerous small compartments. These compartments are lined with a fine network of veins, which are able to expand with blood and to distend and fill up these spaces. When this occurs the whole organ swells and becomes firm and the tension of the fibrous material forming the main structure is called into play so that the process assumes the form of an erection. The veins which should drain the penis of blood are compressed by the action of certain muscles and this adds to the engorgement of the organ.
When the penis of an infant is in a state of erection the operation of circumcision can be more easily performed and the dressing more efficiently applied. The manipulation of the organ necessary to grasp the prepuce is generally sufficient to stimulate the increased blood supply requisite for an erection. The skin of the penis does not share with the rest of the organ, a greater amount of blood during this state. It stretches by its own elasticity.
All the arteries and veins of the penis run in the deep structures previously alluded to, so that circumcision, in an infant at any rate, can never wound a blood vessel. The Frænum is freely supplied with blood, and if cut will produce troublesome hæmorrhage, but a circumcision in no way interferes with this part.
