PENIS. 
just as well in one direction as in another. 
Moreover, when the uterus has been subject to 
irregular spasmodic contractions during the last 
week or two of pregnancy, by which its form 
is more or less altered, we frequently find that 
when labour comes on the child presents with 
the arm or shoulder. It is chiefly to this cause 
that we must attribute those remarkable cases 
which every now and then occur of the arm or 
shoulder presenting in four or five successive 
labours in the same individual, a fact which 
was first pointed out by Professor Naegelé, sen. 
The full-grown living foetus can, therefore, pre- 
sent in only three ways, viz. with the head or 
face, with the nates or inferior extremities, and 
with the arm or shoulder. When other parts 
of the child present, it arises either from its 
having been some time dead in utero or from 
being premature. 
(Edward Rigby.) 
PELVIS.—See SuprpLemeEnt. 
PENIS.—( Membrum virile ; Gree. cevpesoy 
edovov; Germ. das Glied, or die Ruthe; 
Fran. verge ; Ital. membro virile.) 
The term penis would appear from its deri- 
vation (a pendendo) to have been the popular 
designation of the male organ of man and of 
the higher animals among the Roman people. 
Like many other terms that we have received 
from our predecessors, the present has reference 
to a merely visual character of the organ in a 
small group of animals, irrespective of the 
important office which it is intended to fulfil in 
the general animal economy. At the present 
day, however, with a more enlarged scale of 
information with regard to the laws and attributes 
of living beings, while we retain the name, we 
assign to it a more comprehensive definition than 
its original application was intended to convey. 
The penis, throughout the animal kingdom, 
is the organ of transmission of the male fluid 
to the germinal product of the female sexual 
apparatus; and in the mammiferous class it 
performs the additional office of efferent duct 
to the urinary secretion. In consideration of 
its more obvious purpose, the penis has been 
termed the organ of intromission; but this 
appellation, though correct in general, is incor- 
rect in particular instances, for there are many 
among the inferior animals in which a rudi- 
mentary penis exists, but no intromission can 
possibly occur. 
As generation divides its claim with nutrition 
in the lowest animal organisms, we are natu- 
rally led to the expectation of finding the repre- 
sentative of this organ among the lowest divisions 
_ of the animal scale, and this expectation is 
realized by research. In proceeding to this 
_ investigation, however, it cannot too strongly 
_ be impressed upon the mind, that in the lowest 
even as in the highest, modifications do occur 
which are conformable to the wants or conve- 
nience of the animals in whom they are found, 
without reference to any supposed gradation of 
developement or improvement. Thus in Infu- 
_soria a sexual apparatus consisting of ovary, 
testis, and vesicule seminales, has been de- 
909 
scribed by Ehrenberg; and in Rotifera the 
same author has observed a contractile organ 
which serves to impel the seminal fluid into 
the oviduct. Here, then, almost on the boun- 
dary line of the animal world, is a self-impreg- 
nating animal, provided with a distinct trans- 
mittent organ by which impregnation is effected. 
But remarkable as this conformation may appear 
at first sight, examples equally wonderful 
become multiplied as we proceed onwards in 
our enquiry. 
Bory St. Vincent has pointed out the existence 
of an intromittent spiculum in the Vinegar Eel 
(anguillula aceti), one of the Vibrionide; and 
Ehrenberg has observed a similar structure in 
another species, the Anguillula fluviatilis. 
Among the Cestoid Entozoa, which are andro- 
gynous, a distinct intromittent organ is found 
in Ligula and Tenia solium. In Trematoda, 
which are likewise androgynous, but impregnate 
by mutual ‘concurrence, a penis is also met 
with, and is of considerable size. In Acantho- 
cephala, the large intromittent organ of Echi- 
norynchus gigas, the entozoon of the kidney, 
has been described by Cloquet; and in Nema- 
toidea the penis has attained a size and impor- 
tance which renders it a generic character. 
Thus the genus Filaria is distinguished from 
Trichoceplalus by a difference in form of the 
preputial covering, and a similar character 
distinguishes Ascaris from both the preceding. 
Most of the smaller species of Ascaris are 
remarkable, from possessing a double intro- 
maittent organ, and a similar conformation is 
met with in Linguatula, the entozoon of the 
frontal sinuses of the canine race; in Cucul- 
lanus, and in Syngamus trachealis, the tracheal 
parasite of gallinaceous birds. 
Proceeding a step higher in the ai-imal scale 
we find in the class Annelida that the organs 
of generation are hermaphrodite, and so dis- 
posed as to admit of mutual impregnation. 
In some genera the penis is well developed 
and distinct, as in Planaria and Hirudo; but 
in others the mutual apposition of the sexes is 
so perfect as to render an intromittent organ 
unnecessary. On this principle the penis is 
absent in the Earth-worm. In the Leech the 
penis is long and slender, placed on the twenty- 
fourth segment of the body, while the vulva 
occupies the twenty-ninth. 
In Cirrhopoda, the barnacles or-acorns of the 
sea, the intromittent organ is well developed, 
and from the mode of existence of these animals 
and their hermaphrodite organization, may be 
employed as a means of self or of reciprocal 
impregnation. 
The class Crustacea is composed of animals 
which are dicecious in their sexual organization, 
and whose males are provided with a distinct 
intromittent organ. In the lowest groups, 
namely, the Entomostracous Lernez, the penis 
is double; and in Decapoda and Brachiura it 
is temporary and formed by an eversion of the 
vas deferens, an adaptation of means to an end 
that we shall find repeated among the lower 
classes of Vertebrata. Throughout the whole 
of this class impregnation is effected by reci- 
procal union. 
