ANATOMY. 
mg into that canal is extremely small, while 
the communication with the vesicula is large 
and tree. Hence it has been supposed that 
these vesicles are reservoirs for retaining 
the fluid formed in the testicles until it is 
wanted. 
Prostrate gland . — The origin of the ure- 
thra is surrounded by the substance of this 
gland, which in size and form much resem- 
bles a chesnut. Numerous openings are 
found in the commencement of the urethra, 
which discharge on pressure a whitish viscid 
fluid, secreted in the substance of the pros- 
tate. A portion of the gland projects into 
the lower part (if the commencement of the 
urethra, and has received the name of caput 
gallinaginis : it is on this that the openings 
of the canals, formed by the junction of the 
vasa deferentia and vesiculse seminales are 
found. 
The urethra is subservient to two pur- 
poses ; the expulsion of the semen in the 
act of copulation ; and the conveyance of 
the urine from the bladder. Its surface is 
perfectly smooth, and is covered and pro- 
tected by a mucous secretion. The diame- 
ter of this canal varies slightly at different 
parts, but may be stated generally at about 
one-eighth of an inch. At its first depar- 
ture from the bladder, it is surrounded for 
one inch by the prostate ; it is then conti- 
nued as a simple membranous tube, but sur- 
rounded by muscular fibres for another 
inch ; this is called the membranous portion 
of the urethra. In the rest of its passage it 
is surrounded by a vascular substance, call- 
ed corpus spongiosum ; this is accumulated 
in a considerable mass at its commence- 
ment, where indeed the urethra is broader 
than in any other situation, and this is call- 
ed the bulb. The seminal and prostatic li- 
quors are poured into the bulb of the ure- 
thra, and are forcibly expelled from thence 
by a sort of convulsive contraction of a 
muscle, whose fibres surround this part of 
the canal; the ejaculator seminis. The 
glans penis is nothing more than a portion 
of tlie same vascular mass, which surrounds 
the rest of the urethra, covered by a very 
delicate, sensible, and finely organized inte- 
gument. 
The bulb, corpus spongiorum, and glans, 
are susceptible of the same erection as the 
body of the penis ; which is indeed essen- 
tial to the performance of their functions, 
in conveying the fecundating liquor into the 
body of the female. 
The penis consists of two "bodies, called 
crura or corpora cavernosa, which arise se- 
parately from the bones of the pelvis ; but 
join so as to form afterwards a single organ. 
Each crus consists of a very strong and dense 
ligamentous tube, filled internally' with cel- 
lular substance, into the cells of. which the 
arteries open, and from which the veins 
commence. The arteries pour the blood 
into these organs with great energy, in obe- 
dience to the passions of the mind, and 
thereby distend the ligamentous tubes until 
they feel perfectly hard and rigid, in 'which 
state the whole organ is fitted for the func- 
tion which it has to perform in the act of 
copulation. The. urethra, surrounded by 
its spongy substance, runs along the under 
surface of the corpora cavernosa, and the 
glans penis is situated at the anterior extre- 
mity of these parts. 
The body of the penis is covered by com- 
mon integuments, which being adapted to 
cover the organ in its extended state, fall 
into wrinkles when it is collapsed. These 
. are continued beyond the end of the glands, 
and are inflected, so as to form a hood or 
covering to the glans, called the prepuce. 
The latter part is connected to the mouth 
of the urethra by a small fold named the 
frenum. The surface of the glans, and the 
lining of the prepuce are smeared with an 
unctuous matter of peculiar odour, furnished 
by some small glands. 
OF THE BRAIN AND NERVES. 
The brain is a soft and somewhat white 
substance, situated in the cavity of the 
skull, and corresponding in form to that ca- 
vity. Its parts are supported by a firm 
membrane, called the dura mater, and its 
substance is more immediately invested by 
a delicate membrane, called the pia mater. 
The structure of the brain is remarkably 
constant and uniform ; very seldom deviat- 
ing from the accustomed standard. Varie- 
ties of formation occur, not unfrequently, 
in most other parts of the body ; but the 
parts of the brain preserve an almost invari- 
able relation of form, position, magnitude, 
and connection ; which seems to prove, that 
the right performance of the functions of 
this organ requires an exactness in the 
structure of individual parts. 
According to Scemmerring, the weight of 
the brain varies from 2/6. 5§ oz. to 3/6. oz. 
Of two hundred brains, which this anato- 
mist examined, none weighed four pounds, 
whereas Haller states its weight as amount- 
ing in general to five pounds. The weight 
of the brain, compared to that of the body, 
is in an inverse ratio to the age of the sub- 
