. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Preservation of Species 477 Among birds there is no true copulation, but impregnation by the method of the cloacal kiss is the general rule. There are, however, a few birds, notably ostriches and other ratitates, certain ducks, and the South American "tinamou," which have ââ«â¢- Dorsal Veins, Arteries, and Nerves "Corpora Cavernosa â "Blood Vessels âIntegument âUrethra âCorpus Spongiosum Fig. 399. Transverse section through middle
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Preservation of Species 477 Among birds there is no true copulation, but impregnation by the method of the cloacal kiss is the general rule. There are, however, a few birds, notably ostriches and other ratitates, certain ducks, and the South American "tinamou," which have ââ«â¢- Dorsal Veins, Arteries, and Nerves "Corpora Cavernosa â "Blood Vessels âIntegument âUrethra âCorpus Spongiosum Fig. 399. Transverse section through middle of human penis. (After Toldt.). well-developed penes, resembling those of crocodiles. The penis in all mammals, with the exception of monotremes (Fig. 398b), is a closed tube and not a grooved structure as in reptiles. In- termediate forms between reptiles and mammals are not known. It is typically a turgescent organ under the control of vaso-dilator nerves which arise as autonomic fibers in the sacral region of the spinal cord, and is composed of two masses of erectile tissue side by side, the corpora caver- nosa, with a third similar mass, the corpus spongiosum beneath them, held together by fibrous tissue and enveloped by a layer of loose skin (Fig. 399). The corpus spongiosum is perforated for its entire length by the urethra. Consequently the urethra is considerably longer in the male than in the corresponding female. It terminates in an en- largement of the corpus spongiosum called the glans (Fig. 398d), which is split in marsupials where the female has a double vagina. In some animals, for example the cat, guinea pig, and wombat, the glans is beset with horny recurrent spines or corneal scales that stimulate the female during copulation, although in most cases the skin extending over the surface of the glans is extremely sensitive and delicate without any hard corneal layer. Ruminants, cetaceans, and some rodents are exceptional in that there is no glans presen
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
