PENIS. 
meatus; it terminates by several ramified ducts 
in the submucous tissue of the canal. The 
mucous membrane of the urethra is separated 
from the tissue of the corpus spongiosum by a 
moderately thick fibrous layer, which is conti- 
nuous with the external tunic of the spongy 
body. 
Sir Everard Home conceived that the exter- 
nal tunic of the canal of the spongy portion of 
the urethra was muscular, and states with re- 
gard to it: “the muscular covering by which 
the membrane is surrounded or enclosed is 
made up of fasciculi of very short fibres, which 
appear interwoven together and to be connected 
by their origins and insertions with one another; 
they have all a longitudinal direction.” ‘“ The 
fasciculi are united together by an elastic sub- 
stance of the consistence of mucus.” Sir E. 
Home is mistaken with regard to the muscu- 
larity of the external tunic of the spongy urethra, 
but his description, as it relates to the disposi- 
tion of the fibrous tissue, is correct. Indeed it 
is evident that it is to this tissue that Sir E. 
Home alludes, from a subsequent passage in 
his essay, wherein he identifies his muscular 
coat with the fibrous lining of the canal of the 
corpus spongiosum. Thus he writes: “ Im- 
mediately beneath the muscular portion of the 
urethra is the cellular structure of the corpus 
spongiosum.” And this inference is still fur- 
ther corroborated by his belief that the external 
' fibrous tunic of the corpus cavernosum has also 
‘an admixture of muscular fibres.” 
The muscles of the penis are, the erectores 
penis, acceleratores urine, ischio-bulbosi, and 
compressores vene dorsalis. 
The erector penis (m. ischio-cavernosus) is 
the muscle of the corpus cavernosum. It arises 
by tendinous fibres from the anterior part of the 
tuber ischii, from the internal border of the 
ramus of the ischium, and from the root of the 
crus penis ; it then curves in an oblique direc- 
tion around the corpus cavernosum, and termi- 
nates partly by becoming inserted into the side 
of that body, and partly by a tendinous apo- 
neurosis, which is continuous with a similar 
aponeurosis derived from the opposite muscle. 
In the first part of its course the muscle is ten- 
dinous; where it is spread out on the crus 
penis and corpus cavernosum it forms a thin 
fleshy layer, which is prolonged for about one- 
third along the penis, while in the rest of its 
extent it is again tendinous, and constitutes the 
thin aponeurosis above described. The erector 
pe appears to effect its action as an erector 
y compressing the crura and vena dorsalis, 
and is aided in this office by the connection of 
its aponeurosis by means of the suspensory 
ligament with the symphysis pubis. When 
called into exercise both muscles act together, 
and by their united action embrace the root of 
the penis, and strongly compress it. The effect 
of pressure on the vena dorsalis must obviously 
be to impede the return of the venous blood 
from the penis, and the compression of the 
crura produces the same result on the veins of 
the corpus cavernosum. 
The acceleratores uring (m. bulbo-caverno- 
sus) are the muscles of the corpus spongiosum ; 
915 
they are situated on the posterior third of that 
body, and form a thin muscular plane which 
surrounds its cylinder, and is spread out upon 
the under surface of the bulb. Each muscle 
arises from the posterior border of the deep 
perineal fascia at the middle line, and from a 
median raphé which is closely adherent to the 
under surface of the bulb and corpus spongio- 
sum, and which connects it with its fellow of 
the opposite side. From this extensive origin 
the fibres of the muscle pass obliquely out- 
wards and forwards, the most posterior to be 
inserted into the ramus of the ischium and 
pubis, the middle and most numerous to en- 
circle the corpus spongiosum, and uniting by 
tendinous fibres with the muscle of the opposite 
side upon the upper surface of that body, to be 
inserted into the inferior groove of the corpus 
cavernosum ; and the anterior forming a narrow 
fasciculus to pass outwards upon the corpus 
cavernosum and be inserted into its fibrous 
tunic and into the fascia penis. The posterior 
fibres are almost transverse in their direction, 
and cross the triangular interval between the 
bulb and crus penis, being separated from the 
deep perineal fascia by the superficial perineal 
vessels and nerve, and by the ischio-bulbosus 
muscle when it exists. 
The acceleratores are well calculated to con- 
tract forcibly the canal of the urethra, and thus 
to communicate an expulsive impetus to the 
stream of urine or seminal secretion passing 
along the tube. The expulsive action of these 
muscles is made sensible to the hand when we 
withdraw a catheter; and the strength of its 
gripe, when the catheter has been lodged in 
the bladder. Indeed their complete contraction 
constitutes an impassable though temporary 
obstruction to the passage of the catheter along 
the urethra, and gives rise to that form of 
impediment which is known by the name of 
spasmodic stricture. The contraction of these 
muscles, moreover, acting suddenly on the 
urethra, serves to expel the last portions of 
urine and seminal secretion. Besides the in- 
fluence which they exert on the urethra, the 
acceleratores urine also enact the part of erec- 
tors of the penis, by producing so much pressure 
on the bulb and posterior part of the corpus 
spongiosum as may impede the return of blood 
through the ven corporis spongiosi, and at 
the same time press forwards the contents of 
the venous plexus of the bulb into the anterior 
part of the corpus spongiosum and glans penis ; 
and their action in this respect is increased by 
the tension made by their anterior fasciculi on 
the fascia penis, and through it on the vena 
dorsalis. 
The ischio-bulbosus (m. transversus perinei 
alter; m. transversus perinei profundus) is a 
small fan-shaped muscle situated in the trian- 
gular interspace between the bulb of the urethra 
and crus penis, and is not unfrequently want- 
ing. It arises by a pointed origin from the 
ramus of the ischium, and passing obliquely 
inwards across the triangular space above des- 
cribed, spreads out into a thin fan-shaped plane, 
and is inserted into the fibrous tunic of the 
bulb. On one occasion I found this muscle 
3.N 2 
