After the infliction of a wound upon the artery, the blood may escape at once directly through the external wound; if pressure be now made upon the wound, the general diffusion of the blood may be prevented, and a process of thickening may be set up in the areolar membrane surrounding the small quantity of blood which has insinuated itself between the wound in the artery and the integuments; this thickened areolar membrane becomes matted together by the effusion of coagulable lymph, and is ultimately converted into the cyst of the aneurism, which communicates with the canal of the wounded artery: this has been termed a circumscribed false aneurism.