. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. RBPRODUOTION. 89 ire or leas of the ui that described. LWgmte). e, embryo; eal TMicle; a, •mnion: I the total portion of aeeidu vera; a. r, ut some rupture scularity of the I of this structure ' to great advan- method also the tmbranes can be to and ttom the placenta are reduced to three, two arteries and one vein. The villi of the placenta (chorion) are usually said to hang free
. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. RBPRODUOTION. 89 ire or leas of the ui that described. LWgmte). e, embryo; eal TMicle; a, •mnion: I the total portion of aeeidu vera; a. r, ut some rupture scularity of the I of this structure ' to great advan- method also the tmbranes can be to and ttom the placenta are reduced to three, two arteries and one vein. The villi of the placenta (chorion) are usually said to hang freely in the blood of the large irregular sinuses of the decidua sero- tina; but this is so unlike what prevails in other groups of animals that we can not refrain from believing that the state- ment is not wholly true. The Zonary FlMsenta.—In this tjrpe the placenta is formed along a broad equatorial belt, leaving the poles free. This form of placentation is exemplified in the camivora, hyrax, the ele- phant, etc. In the dog, for example, the yelk-sac is large, vascular, does not fuse with the chorion, and persists throughout A rudi- mentary discoid placenta is Brst formed, as in the rabbit; this gradually spreads over the whole central area, till only the ex- tremes (poles) of the ovum remain free; villi appear, fitting into pits in the uterine surface, the maternal and foetal parts of the placenta becoming highly vascular and closely approximated. The chorionic zone remains wider than the placental. As in man there is at burth a separation of the maternal as well as foetal part of the placenta—i. e., the latter is deciduate; there is also the beniming of a decidua reflexa. The Dimue PlMenta.—As found in the horse, pig, lemur, etc., the allantois completely incloses the embryo, and it be- comes villous in all parts, except a small wea at each pole. The Fdlyootyledoiiaxy FlMenta.—This form is that met with in ruminants, in which case the allantois completely covers t
Size: 984px × 2538px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthormillswes, bookcentury1800, bookdecade1890, bookyear1890
