Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . The common fowl,or goose, form excellent subjectsfor study, and they can always beprocured in a fresh state. Fig. 187represents the gastric glands in theglandular layer of the proventricu-lus of the common fowl; A is thegland of its natural size, and B is amagnified representation of thesame, where the caeca appear likeclusters of berries attached to astem. In young birds the cellularstructure of these glands is veryconspicuous. Fig. 188,
Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . The common fowl,or goose, form excellent subjectsfor study, and they can always beprocured in a fresh state. Fig. 187represents the gastric glands in theglandular layer of the proventricu-lus of the common fowl; A is thegland of its natural size, and B is amagnified representation of thesame, where the caeca appear likeclusters of berries attached to astem. In young birds the cellularstructure of these glands is veryconspicuous. Fig. 188, at A, areseen the simple gastric glands of ayoung owl, of the natural size; andat B, the same magnified, to shewthe cellular structure of these organs. The relation in whichthese glands stand to the secretion of the gastric juice is not yetsatisfactorily ascertained; the microscope shows that the orifices,and inner lining of the glands, are covered with a fine tessellatedepithelium, whilst the parenchyma of the gland consists ofminute granular corpuscules, about 1-200th of a line in dia-meter, not always nucleated, but formed of an uniform granular. 182 ORGANS OF DlitESTIOtf. mass, rather than of elements having a cellular character; thewall of the gland is formed of a transparent structureless mem-Pig. 184. brane- Be~ sides these granular cor-puscles an al-buminousfluid exudesfrom the wallsof the sto-mach, andmingles withthat yieldedby the gastricglands ; thegastric juiceappears to beloaded withcorpuscles,having a pe-culiar acidmixed with it,secreted by tt an appropri-ate set orglands, fromwhich it isexpressed bythe contrac-tion of the muscular coat of the stomach, when excited intoaction by the presence of food.—T. W.] § 331. The result of this process is the reduction of thefood to a pulpy fluid called chyme, which varies in its naturewith the food. Hence the function of the stomach has beennamed chymification. With this the function of digestion iscomplete in many of th
Size: 893px × 2798px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1870
