ORGANS OF GENERATION. 



423 



powerful muscular sheath, calculated to en- 

 sure the expulsion of the fluid which they 

 elaborate. 



The most remarkable arrangement of Cow- 

 per's glands is seen in the Ichneumon ( Her- 

 pestes Ichneumon, Illiger): in this animal they 

 are very large and occupy their usual position, 

 being invested with a strong muscular coat; 

 but their excretory ducts, instead of termi- 

 nating as usual in the bulbous portion of the 

 urethra, are prolonged beneath the penis nearly 

 to the extremity of that organ, where they 

 open into a cul-de-sac common to them and 

 the canal of the urethra. 



Accessory vesicles. These are auxiliary 

 glands, which pour their secretions into the 

 canal of the urethra. They appear, when 

 present, to take the place of the prostate, 

 being only found where that organ is deficient, 

 and accordingly, although of a totally different 

 structure from that body, they have been called 

 prostates by various authors. They are usually 

 packets of membranous cceca, more or less ra- 

 mified, and in the season of sexual excitement 

 are filled with a fluid resembling that contained 

 in the vesiculae seminales. These organs exist 

 in all Rodents except Squirrels, Marmots, and 

 Hares, and also in the Hedgehog and the 

 Mole, but have not been found in any other 

 mammalia. They are invariably composed 

 of intestinules or branched coeca, arranged in 

 packets, the number of which varies much. 

 Thus in the Mole there are five such bundles, 

 forming a mass of ramified tubes larger than 

 the bladder ; in the Hedgehog there are four, 

 and in Cricetus vulgaris and Dasyprocta 

 Aguti two fasciculi. 



But besides the secreting structures above 

 enumerated as forming the ordinary appendages 

 to the male generative system of Mammifers, 

 additional ones are occasionally found, placed 

 out of the positions in which the succenturiate 

 glands usually exist. Thus in Solipeds a long 

 coecum containing a glairy fluid is placed be- 

 tween the insertions of the vasa deferentia, 

 which communicates with the urethra by an 

 appropriate orifice ; and in Cricetus and many 

 of the JMuridtE the ends of the deferent canals 

 before their termination are provided with 

 bunches of small glandular follicles, which in 

 the former resemble small bunches of grapes. 



Fig. 208. 



The annexed figure, (fig. 208,) representing 

 the male generative viscera of the Rat ( Mus 

 Ruttus) exhibits an example of the greatest com- 

 plication of these parts, and will serve to illus- 

 trate the situation of the organs above described. 

 A represents the bladder turned forwards, B the 

 rectum, and C the testis of the left side. The 

 succenturiate glands here found are , a, the 

 vesicu/te seminales ; 6, the anterior fasciculus of 

 the accessory vesicles or anterior prostate of 

 some authors, which on the opposite side is un- 

 ravelled to display the cceca which compose it ; 

 c, the middle prostatic coeca; d, the anterior 

 prostatic coeca. These all communicate with 

 the urethra, and in addition to these we have 

 on each side the racemose bunch of follicles (e) 

 which is appended to the termination of the 

 vas deferens (./"). 



Structure of the penis. The great difference 

 between the penis of Mammifers and that which 

 has been described as existing in the oviparous 

 vertebrata, consists in theinclosure of the canal 

 of the urethra, which is no longer a simple 

 groove formed by the junction of the corpora 

 cavemosa, but becomes surrounded with a cy- 

 linder of erectile tissue usually denominated 

 the corpus spongiosnm urethra. The corpus 

 cavernosum, which generally forms the great 

 bulk of the organ, arises by two crura, which are 

 firmly attached to the rami of the ischium in 

 the males of all placental Mammalia; and even 

 in the Cetacea, where there is no pelvis, two 

 bones placed on each side of the corpus caver- 

 nosum give a support to the penis, which is 

 attached to them by fibrous ligaments; never- 

 theless, in the Marsupiata the crura of the 

 corpus cavernosum are quite free, or only 

 loosely attached to the ischiadic bones by 

 the muscular sheaths in which they are en- 

 veloped. The crura of the corpora cavernosa 

 unite to form the body of the penis, their 

 union being generally marked by a strong 

 septum, which more or less completely divides 

 the organ into two lateral halves. In some 

 animals, as in the Dog, this septum is very 

 distinct ; but in other cases, especially in many 

 of the Plantigrade Carnivora and in most of the 

 Pachydermatous and Cetaceous tribes such a 

 partition is entirely wanting; in such cases the 

 fibrous lamellae, which arise from the dense 

 capsule surrounding this portion of the penis, 

 and traverse the vascular tissue which is con- 

 tained in its interior, unite at a central part in 

 a kind of cord formed by their union. In 

 some animals the organ is supported by a bone 

 developed in its interior: this arrangement 

 exists in the Quadnmuma, Cheiroptera, the 

 Plantigrade and Digitigrade Carnivora (ex- 

 cept the Hyaena), and in the Rodentia, also in 

 Seals and Cetaceans. In a few instances it is 

 so large as to form a large portion of the penis, 

 as in Whales ; in others, as in many Carnivora 

 and Rodentia, it is extremely small, but what- 

 ever its form or size it is invariably found in- 

 timately connected with the corpus caverno- 

 sum. 



The urethra, as in man, consists of a mus- 

 cular and of a vascular portion, the former 

 receiving the ducts of the succenturiate and 



