. Biology . urther function of preventing a surplus of CO2 in the blood. The Crop and Gizzard.—In the 14th segment the digestivetract enlarges to form a thin-walled expansion called the crop,extending from the 14th to the i6th somites. No special func-tion, apart from storage, is attributed to this organ, but it opensdirectly into a thick-walled gizzard provided with powerfulcircular muscles. The contraction of these muscles, acting onthe contained food material mixed with gravel, results in thetrituration of the solid food materials and prepares them fordigestion in the stomach intestine. The
. Biology . urther function of preventing a surplus of CO2 in the blood. The Crop and Gizzard.—In the 14th segment the digestivetract enlarges to form a thin-walled expansion called the crop,extending from the 14th to the i6th somites. No special func-tion, apart from storage, is attributed to this organ, but it opensdirectly into a thick-walled gizzard provided with powerfulcircular muscles. The contraction of these muscles, acting onthe contained food material mixed with gravel, results in thetrituration of the solid food materials and prepares them fordigestion in the stomach intestine. The Stomach Intestine.—This, the most important organ ofthe alimentary system, begins at about the i8th somite and runs DIGESTIVE SYSTEM OF THE EARTHWORM 141 in a straight course to the posterior end of the worm. It consistsof epithehal, vascular, circular and longitudinal muscular tissuesand is covered on the outside by peculiar yellowish-brownchlorogogue cells, derived from the coelomic endothelium. Along. Fig. 55-—Stereogram showing the relations of organs in the posterior part ofthe earthworm. (Worked out by Professors McGregor and Calkins, and drawnby Miss Hedge.) the dorsal median line a longitudinal fold of tissue coming fromthe dorsal wall of the intestine runs the entire length of thisorgan as far as the rectum. This fold, called the typJilosole(Fig. 55), has a different form in different regions of the bodyand contains additional blood vessels and chlorogogue cells,thus increasing the area of the digestive surface. The intestine, 142 ORGANS AND ORGAN SYSTEMS finally, is constricted at each dissepiment so that its structurefollows the general metamerism of the body. The digestive fluid secreted by the wall cells of the intestinecorresponds in its essential features with the pancreatic juiceof mammals. Free acids cannot be detected in the gut,where the fluids in general show a slightly alkaline to Lesser and Taschenberg, albumin is broken downunder
Size: 1509px × 1656px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectbiology
