. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine . .—Diagrams illustrating development of pronephron in the fowl (Ilnddon).ao, aorta; , body-cavity; ep, epiblast with its epitrichial (flattened) layer; hy,hypoblast; m. s, mesoblastic somite; n. c, neural canal; nch, notochord; p. , pro-nephric tubule; so, somatic, and up, splanchnic mesoblaBt. THE DEVELOPMENT OF THE EMBRYO ITSELF. H3 opsida (fishes and amphibians). A vascular process from theperitoneum (glomerulus) projects into a dilated section of thebody cavity, which is in pa
. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine . .—Diagrams illustrating development of pronephron in the fowl (Ilnddon).ao, aorta; , body-cavity; ep, epiblast with its epitrichial (flattened) layer; hy,hypoblast; m. s, mesoblastic somite; n. c, neural canal; nch, notochord; p. , pro-nephric tubule; so, somatic, and up, splanchnic mesoblaBt. THE DEVELOPMENT OF THE EMBRYO ITSELF. H3 opsida (fishes and amphibians). A vascular process from theperitoneum (glomerulus) projects into a dilated section of thebody cavity, which is in part separated from the rest of thiscavity (ccelom). This process, together with the segmental duct,now coiled, and certain short tubes developed from the originalduct, make up the pronephros. The segmental duct opens atlength into the cloaca. The mesonephros (Wolffian body), though largely developedin all vertebrates during fcetal life, is not a persistent excretoryorgan of adult life. In the fowl recent investigation has shown that the Wolffian(segmental) tubes originate from outgrowths of the Wolffian. Fig. 120. Fig. 181. Fig. 120.—Rudimentary primitive kidney of embryonic dog. The posterior portion ofthe body of the embryo is seen from the ventral side, covered by the intestinallayer of the yelk-sac. which has been torn away, and thrown back in front inorder to show the primitive kidney ducts with the primitive kidney tubes (a), h,primitive vertebrae; c, dorsal medulla; d, passage into the pelvic intestinal cavity.(Hacckel. alter Bischoff.) Fig. 121.—Primitive kidney of a human embryo, v. the urine-tubes of the primitivekidney: ir. Wolffian duct; w, upper end of the latter (Morgagnis hydatid*: m,Mfillerian duct; m. upper end of the latter (Fallopian hydatid): g, hermaphrodite> gland. (After Kobelt.) duct aud also from an intermediate cell-mass, from which latterthe Malpighian bodies take rise. The( tubes, at first not con- 114 COMPARATIVE PHYSIOLOGY. nected with the
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