. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. Fig. 41. Ichthyosauran coprolites, one in section. The spiral character b taken as evidence of the presence of a spiral valve in these reptiles. After found higher in the scale.^ In the higher fishes it is replaced by cascal tubes (pyloric appendages) developed close to the pylorus. The number of these varies from one in cer- tain ganoids to over one hundred and fifty in the mackerel. In the amphibia and reptiles the mid gut is nearly straight in the elongate forms, more convoluted in the shorter types, the convolut
. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. Fig. 41. Ichthyosauran coprolites, one in section. The spiral character b taken as evidence of the presence of a spiral valve in these reptiles. After found higher in the scale.^ In the higher fishes it is replaced by cascal tubes (pyloric appendages) developed close to the pylorus. The number of these varies from one in cer- tain ganoids to over one hundred and fifty in the mackerel. In the amphibia and reptiles the mid gut is nearly straight in the elongate forms, more convoluted in the shorter types, the convolutions increasing in extent in the birds and mammals. In the birds, at about the mid- dle, the mid gut bears a blind tube, the vitel- line caecum, the remains of the yolk stalk of development, by which, in the earlier stages, the intestine was connected with the volk. In these higher forms increase of intestinal sur- face is brought about in part b}' the lengthening of the intes- tine, and in part by the development of numerous small folds (valvulae conniventes) and minute finger-like projec- tions (villi) resembling the pile of velvet. The hind gut is hardly distinct in fishes, as viewed externall)-, but from the amphibia on it acquires greater individualit}-. It may consist merely of a straight tube, rectum, or it may have a terminal rectum connected with the mid gut by a more or less convoluted tube, — the colon. Just behind'the ileo- colic valve in the forms from the turtles upwards is developed a 1 The marks on certain reptilian coproUtes indicate that some reptiles may have had a spiral valve (Fig. 41). Fig. 42. Stom- ach and pyloric caeca of Salmo, after Rathke. 7, intes- tine; P, pyloric caeca; S, 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 Kingsley, J. S. (John Sterling), 1854
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