Description of plate 47.

A. The aorta at its point of bifurcation.

B. The anterior superior iliac spine.

C. The symphysis pubis.

D. Poupart's ligament, immediately above which are seen the circumflex ilii and epigastric arteries, with the vas de­ferens and spermatic vessels.

E E*. The right and left iliac muscles covered by the perito­naeum; the external cutaneous nerve is seen through the membrane.

F. The vena cava.

G G*. The common iliac arteries giving off the internal iliac branches on the sacro-iliac symphyses; g g, the right and left ureters.

H H*. The right and left common iliac veins.

I I*. The right and left external iliac arteries, each is crossed by the circumflex ilii vein.

K K *. The right and left external iliac veins.

L. The urinary bladder covered by the peritonaeum.

M. The rectum intestinum.

N. The profundus branch of the femoral artery.

O. The femoral vein; 0, the saphena vein.

P. The anterior crural nerve.

Q. The sartorius muscle, cut.

S. The pectinaeus muscle.

T. The adductor longus muscle.

U. The gracilis muscle.

V. The tendinous sheath given off from the long adductor muscle, crossing the vessels, and becoming adherent to the vastus internus muscle.

W. The femoral artery. The letter is on the part where the vessel becomes first covered by the sartorius muscle.

Plate 47.

COMMENTARY ON PLATES 48 & 49.

THE RELATIVE ANATOMY OF THE MALE PELVIC ORGANS.

As the abdomen and pelvis form one general cavity, the organs contained in both regions are thereby inti­mately related. The viscera of the abdomen com­pletely fill this region, and transmit to the pelvic organs all the impressions made upon them by the diaphragm and abdominal walls. The expansion of the lungs, the descent of the diaphragm, and the con­traction of the abdominal muscles, cause the abdominal viscera to descend and compress the pelvic organs; and at the same time the muscles occupying the pelvic outlet, becoming relaxed or contracted, allow the perinaeum to be protruded or sustained voluntarily accord­ing to the requirements. Thus it is that the force originated in the muscular parietes of the thorax and abdomen is, while opposed by the counterforce of the perinaeal muscles, brought so to bear upon the pelvic organs as to become the principal means whereby the contents of these are evacuated. The abdominal muscles are, during this act, the antagonists of the diaphragm, while the muscles which guard the pelvic outlet become at the time the antagonists of both. As the pelvic organs appear therefore to be little more than passive recipients of their contents, the voluntary processes of defecation and micturition may with more correctness be said to be performed rather for them than by them. The relations which they bear to the abdomen and its viscera, and their dependence upon these relations for the due performance of the pro­cesses in which they serve, are sufficiently explained by pathological facts. The same system of muscles comprising those of the thorax, abdomen and peri­naeum, performs consentaneously the acts of respira­tion, vomiting, defecation and micturition. When the spinal cord suffers injury above the origin of the phrenic nerve, immediate death supervenes, owing to a cessation of the respiratory act. Considering, how­ever, the effect of such an injury upon the pelvic organs alone, these may be regarded as being absolutely excluded from the pale of voluntary influence in consequence of the paralysis of the diaphragm, the abdominal and perinaeal muscles. The expulsory power over the bladder and rectum being due to the opposing actions of these muscles above and below, if the cord be injured in the neck below the origin of the phrenic nerve, the inferior muscles becoming para­lysed, the antagonism of muscular forces is thereby interrupted, and the pelvic organs are, under such circumstances, equally withdrawn from the sphere of volition. The antagonism of the abdominal muscles to the diaphragm being necessary, in order that the pelvic viscera may be acted upon, if the cord be injured in the lower dorsal region, so as to paralyse the abdo­minal walls and the perinaeal muscles, the downward pressure of the diaphragm alone could not evacuate the pelvic organs voluntarily, for the abdominal mus­cles are now incapable of deflecting the line of force backwards and downwards through the pelvic axis; and the perinaeal muscles being also unable to act in agreement, the contents of the viscera pass involun­tarily. Again, as the muscular apparatus which occu­pies the pelvic outlet acts antagonistic to the abdomen and thorax, when by an injury to the cord in the sacral spine the perinaeal apparatus alone becomes paralysed, its relaxation allows the thoracic and abdominal force to evacuate the pelvic organs involuntarily. It would appear, therefore, that the term "paralysis" of the bladder or rectum, when following spinal injuries, &c. &c. means, or should mean, only a paralytic state of the abdomino-pelvic muscular apparatus, entirely or in part. For, in fact, neither the bladder nor rectum ever acts voluntarily per se any more than the stomach does, and therefore the name "detrusor" urinae, as applied to the muscular coat investing the bladder, is as much a misnomer (if it be meant that the act of voiding the organ at will be dependent upon it) as would be the name "detrusor" applied to the muscular coat of the stomach, under the meaning that this were the agent in the spasmodic effort of vomiting.