. The American journal of anatomy. of the stomachis lined by stratified epithelium and is without glands. An examination of the schemes presented in the foregoing pages re-veals a number of interesting facts, to some of which attention hasbeen already directed by Oppel and others. The first fact that strikes oneis that in all these orders exceptthe Ungulata, individuals exist,the stomachs of which closely re-semble in structure those ofmany existing Camivora, Insec-tivora and Primates. There are good reasons forsupposing that these stomachsrepresent a persistent primitivecondition. They corres
. The American journal of anatomy. of the stomachis lined by stratified epithelium and is without glands. An examination of the schemes presented in the foregoing pages re-veals a number of interesting facts, to some of which attention hasbeen already directed by Oppel and others. The first fact that strikes oneis that in all these orders exceptthe Ungulata, individuals exist,the stomachs of which closely re-semble in structure those ofmany existing Camivora, Insec-tivora and Primates. There are good reasons forsupposing that these stomachsrepresent a persistent primitivecondition. They correspondclosely in the relations of thedifferent gland areas with thestomachs of lower specialization inthe stomach of mammals is ac-companied by suppression of ex-isting elements (glands, etc.) aswell as by increasing complexityof structure, and it is thereforeunlikely that primitive condi-tions would be simulated in astomach that has been derivedsecondarily by degenerative orretrogressive processes occurring. Fig. 15. Stomachs of: A. Dasypus; B, Brady-pus (both modified from KlincowstrOm). in an organ already highly specialized. Moreover, in the Ungulata, no existing member of which exhibits aperfectly simple stomach, the nearest approach to this is found in thoseanimals (the pigs in the Artiodactyla, and the tapirs in the Perissodac-tyla) which have been conservative in other respects, as for example,dentition and foot structure. The obvious inference from these facts is that the specialized stom-achs found in many mammals belonging to different orders, have beendifferentiated at a comparatively late period and entirely within the K. E. Bensley 143 limits of the ordinal groups. Any similarity that may exist betweenvarious orders in the direction and nature of this differentiation, isprobably simply a parallelism due to the operation of similar causes. Turning now to the question of the origin of the oesophageal divisionsof the stomach, we find that there
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectanatomy, bookyear1901
