. A manual of zoology. Zoology. 562 CHORDATA chorion Jrondosnm, or diffuse placenta, which occurs in whales, pcrisso- dactylcs and many artiodactyles. On the other hand, the vilH may Ije restricted to certain places, becoming very strong there. This gives rise to cotyledonary, discoidal, or zonary placenta;. To these correspond por- tions of the uterine lining which are distinguished from the rest liy Ijc- coming extremely vascular {uterine placenta). The cotvhdonary placenta (fig. 6io) consists of many small placentar patches, the fy/y/fJoni-(most r'^^M^^x^. Fig. 6io.—Cotylcdonan,' placenta a
. A manual of zoology. Zoology. 562 CHORDATA chorion Jrondosnm, or diffuse placenta, which occurs in whales, pcrisso- dactylcs and many artiodactyles. On the other hand, the vilH may Ije restricted to certain places, becoming very strong there. This gives rise to cotyledonary, discoidal, or zonary placenta;. To these correspond por- tions of the uterine lining which are distinguished from the rest liy Ijc- coming extremely vascular {uterine placenta). The cotvhdonary placenta (fig. 6io) consists of many small placentar patches, the fy/y/fJoni-(most r'^^M^^x^. Fig. 6io.—Cotylcdonan,' placenta and embn'O of cow (from Balfour, after Colin). C, cotyledons of'uterine; C", of foetal placenta; C7;, chorion; V, uterus; y, vagina. ruminants). In the zonary placenta the villous area takes the shape of a girdle or barrel (carnivores, Sircnia), while the discoidal (other mammals) is, as its name indicates, discdike. By the restriction of the nutrient structures to certain regions of the placenta, the corresponding part of the uterus (the zonary or chscoid uterine placenta) is more moditied than is the case with the diffuse or the cotyle<lonary type. AVhile in the latter the placental villi are willnlrawn from the uterine walls without injury to them (Indeciduata), in the case of the zonary or discoidal placenta the superficial part of the mucous lining of the uterus, the dccidna, separates (Deciduata), leaviitg the uterine placenta as a bleeding wound, the hemorrhage beiiig stopped by the energetic muscular contractions of the uterus. Besides the placental structures the higher mammals are characterized by the disappearance of the cloaca, the unpaired vagina, and absence of. 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 Hertwig, Richard, 1850-1937; Kingsley, J. S. (John Sterling), 1854-1929, ed.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
