. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Preservation of Species 459 cavity entirely and come to hang outside in a sac of outpushed skin and muscle known as the scrotum (Fig. 386). According to the degree of migration which the testes have undergone, animals in general may be separated into three groups as follows : first, those in which the testes remain within the confines of the body cavity; second, those in which there is a temporary descent during periods of sexual activity, followed by
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Preservation of Species 459 cavity entirely and come to hang outside in a sac of outpushed skin and muscle known as the scrotum (Fig. 386). According to the degree of migration which the testes have undergone, animals in general may be separated into three groups as follows : first, those in which the testes remain within the confines of the body cavity; second, those in which there is a temporary descent during periods of sexual activity, followed by a withdrawal into the body cavity; and third, those with a permanent descent into the scrotum. To the first group belong all verte- brates below the mammals, and among mammals, monotremes, many insectivores, coneys, elephants, and whales. In the second group are many rodents, some insectivores, civet cats, otters, llamas, bats, camels, and certain apes. Those with a permanent descent of the testes after the fetal period, include marsupials, pinnipeds, most carnivores, ungulates, and primates. -Inguinal Canal ^i^Hi^f DuctUS 1 ....-.:, Coe,om>Wv:./ beferensi" \3\ " / „ /^fi^^-JL c -j-j • VTi^^Tlf"Peritoneum (SMtetfl Epididymis >A "-Testis -^ . 'Av-SSSKSr" Obi iterated Passageway Guber rnacuium. Tunica *J&?m Vaginalis. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Walter, Herbert Eugene, b. 1867; Sayles, Leonard Perkins, 1902-. New York : Macmillan Co.
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
