422 



ORGANS OF GENERATION. 



ejaculated during copulation by a muscular 

 arrangement provided for that purpose ; and in 

 the last place the emission of the fecundating 

 fluid is further provided for by the addition of 

 secondary secretions, which from augmenting 

 its quantity facilitates its ejection. 



We shall proceed to speak of these circum- 

 stances seriatim, examining first, the structure 

 and position of the testis and its duct; secondly, 

 auxiliary glands which add their secretions to 

 the seminal liquor; thirdly, the structure of the 

 penis, and arrangement of the organs of intro- 

 mission. 



We have found in all the classes of verte- 

 brata of which we have hitherto treated, that 

 the testes consisted essentially of blind tubes. 

 In Frogs these sperm-secreting canals were ex- 

 ceedingly short; in other Amphibia they become 

 elongated and flexuous. In Reptiles their 

 length and convolution was still further in- 

 creased, until at length in Birds and Mamma- 

 lia their length is so great, and their delicacy 

 so excessive, that they are with difficulty unra- 

 velled. In all animals the terminations of the 

 seminal tubes are found to be closed, neither is 

 any increase or diminution perceptible in the 

 diameter of one of these vessels throughout its 

 whole course. Another circumstance which, 

 with one or two exceptions, is common to all 

 Mammals, is that they never ramify or divide.* 



Mammalia differ much amongst each other 

 as regards the length, number, convolutions, 

 and general arrangement of these secerning 

 vessels of the testis. In the Ass they are very 

 delicate; of greater diameter in the Cynoce- 

 phalus and larger Carnivora, as well as in the 

 Hog and Rhinoceros. They are very large in 

 the Glires, and in Sciurus their diameter 

 reaches -0-01453 inch (Paris), whilst in the 

 Hedgehog they are only 0-00970 inch. 



The tenuity of the walls of these seminal 

 vessels is extreme, and scarcely applicable by 

 the micrometer; they are united together by a 

 most delicate tissue of capillary bloodvessels, 

 serving to imbue them with that blood from 

 which the semen is separated, which when se- 

 creted accumulates in the cavities of these tubes 

 in readiness for expulsion. 



The testes are very variously situated in the 

 adult state of different mammals. Sometimes 

 they are contained within the abdominal cavity, 

 attached on each side of the spinal column by 

 folds of the peritoneum, as in the ovipara ; at 

 other times they descend into the skin of the 

 groin through the inguinal canal, and not un- 

 frequently are contained in a scrotal pouch 

 formed by the integument behind the pubic 

 arch; and in the Marsupial division, which, 

 when describing the female sexual organs, we 

 shall find to constitute a distinct type of the 

 generative system, they are suspended in front 

 of the pelvis. 



The excretory duct of each testis or vas de- 

 ferens is formed by the junction of the seminal 

 canals of the testis ; it is at first much convo- 

 luted, forming a mass appended to the testicle, 

 denominated the epididymus; and whatever 



* In Sciurus they have been observed to divide 

 dichotoraously. 



may be the position of the testicle, it runs to 

 discharge itself into the canal of the urethra 

 near the commencement of that tube. 



The prostate gland is a secreting body of pe- 

 culiar structure, which, in man, embraces the 

 neck of the bladder, and opens by ten or twelve 

 ducts into the urethra near its commencement. 

 It is very constant in its existence, being found 

 in all orders of Mammalia, excepting, perhaps, 

 the greater number of the Rodentia, the Mole, 

 and the Hedgehog, in which it is apparently 

 replaced by secerning organs of a widely dif- 

 ferent structure; otherwise, the internal organi- 

 zation of this gland is nearly the same in all 

 animals that possess it, consisting essentially 

 of cells, each of which is subdivided into others 

 of extreme minuteness. From these cells the 

 excretory ducts take their rise, and the whole 

 organ may be readily inflated by forcing air into 

 the canals which issue from it: the whole is 

 enclosed in a dense fibrous capsule. In some 

 animals, as the Elephant and Solipeds, the 

 prostate is double or even quadruple, and in 

 this case the centre of each portion has within 

 it a large cavity which communicates with the 

 smaller cells, and gives origin to the excretory 

 tube. 



Cnu-pci-'s glands. These glands in the hu- 

 man subject are two very small bodies situated 

 behind the bulb of the urethra, which furnish 

 minute canals, opening obliquely into theurino- 

 generative canal near its posterior portion ; but 

 minute as they are in man, they are found in 

 other creatures to be much more voluminous, 

 not unfrequently equalling the prostate in size, 

 and in some cases, especially in the Marsupial 

 division, they are increased in number ; thus 

 in the Opossums and Kangaroo-rat there are 

 four, while in the Wombat (Phascolomys), 

 the Kangaroo, and others, even six are found : 

 nevertheless i:i most of the Carnivora, except 

 the Felidae and Hyenas, and in the greater 

 number of Ruminants, Solipeds, Amphibia, 

 and Cetacea, they are deficient. 



The internal structure of Cowper's glands 

 varies. In man and many others they are 

 composed of simple follicles ; in other cases, 

 as in Sciurus, the Marmot and the Hog, they 

 consist of conical sacculi, which exhibit in- 

 ternally a cellular appearance. In the Beaver 

 (Castor Fiber) their texture is spongy, being 

 formed of large cells, divided by septa into 

 smaller ones of extreme minuteness ; those of 

 the Mole are similarly constructed. In Vi- 

 verru Zibetha, the feline tribes and the Hyena, 

 they are made up of separate lobules; and 

 in the Ichneumon these glands are composed 

 of vesicles united by a common duct. In 

 the Hedgehog ( Krinuceus Europaus) they are 

 found in a very singular position, being partly 

 situated beneath the rami of the pubis and 

 ischium, and partly beneath the skin on the 

 inner side of the thigh, being so remote from 

 the other glands that their existence was over- 

 looked by Cuvier. Each gland consists of 

 pyramidal lobules, which, by their apices, 

 give rise to the excretory canals. 



In some of the Marsupiata their minute 

 structure resembles what is found in the Hedge- 

 hog; and each of them is surrounded by a 



