Licence: Public Domain Mark
Credit: Outlines of zoology / by J. Arthur Thomson. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
204/748 (page 170)
![animals, lines the body-cavity and the outside of the gut. As to their function we know that they absorb particles from the intestine, and go free into the body-cavity, whence, as they break up, their debris may pass out by the excretory tubes. When a worm has been made to eat powdered carmine, the passage of these useless particles from gut to yellow-cells, from yellow-cells to body-cavity, and thence out by the excretory tubes, has been traced. Various ferments have been detected in the gut, a diastatic ferment turning the starchy food into sugars, and others—peptic and tryptic— even more important. The wall of the stomach-intestine from without inwards, as may be traced in sections, is made up of pigmented peritoneum, muscles, capillaries, and an internal ciliated epithelium. In the other parts of the gut the innermost lining is not ciliated, but covered with a cuticle. Vascular System.—The fluid of the blood is coloured red with haemoglobin, and contains small corpuscles. Along the median dorsal line of the gut a prominent blood-vessel extends, another (supra-neural) runs along the upper surface of the nerve-cord, another (infra-neural) along the under surface, while two small lateral-neurals pass along each side of this same cord. All these longitudinal vessels, of which the first three are most important, are parallel with one another; the first three meet in an anterior network on the pharynx ; the dorsal and the supra-neural are linked together in the region of the gullet by five or six pairs of pulsatile vessels or hearts. The precise path of the blood is not known, but the distribution of vessels to skin, nephridia, and alimentary canal is readily seen. Respiration is effected by the distribution of blood on the general surface of the skin. Excretory System.—When a worm is fed with carmine particles, these may be taken up from the intestine by the yellow cells, which may pass them into the body-cavity. Finally, the ])articles have been seen passing out by the excretory tubes. There is a pair of these little kidneys, nephridia or segmental organs, in each segment except the first four. Each opens internally into the segment in front of that on which its other end opens to the exterior. They remove little particles from the body-cavity, but](https://iiif.wellcomecollection.org/image/b21958671_0204.jp2/full/800%2C/0/default.jpg)
