Elements of Zoology. Invertebrate; As Taught in the First Term of the Senior Year in Madison University

Elements of Zoology. Invertebrate; As Taught in the First Term of the Senior Year in Madison University

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1886 edition. Excerpt: ... called Annelida, because their bodies are composed of a number of rings. These rings are marked on the outside of the body by lines of depression between the rings; and are always arranged in Va single straight line from the head to the tail. Each ring is a distinct body segment, the separation from other segments being formed by the separation of the muscles of the body walls, for each segment has its own muscles; also by a diaphragm separating the body cavity into as many chambers as there are external rings. In the earth-worm can readily be seen these diaphragms, with the intestine and blood vessels passing through them, as the Oesophagus and blood vessels pass through the single diaphragm in our own bodies. But the full number of diaphragms between the rings will not be found in all worms. 2()6_-The Segments or rings are also distinct from each other by having no common appendages for locomotion. Each ring has its'own appendages, but these are bristles of various forms, never jointed limbs. Each segment often has its own separate gills, sometimes even each segment has its own eyes and ears. The stomach and heart are enlarged in each segment, and there is a nerve ganglion in each. So that a worm seems to be typically almost a oompound animal. 2()7_-T119 Nerves are more concentrated in the head in worms than in any class before studied. The brain is formed of a nerve mass in front of the mouth, and from this brain, two nerve cords run on the ventral surface the length of the body, with ganglia in each body segment. From these are given ofl' branches which supply all the parts of the body. The senses of sight and hearing and touch are very perfect in the higher worms. 208__The Heart is a tubular vessel on the dorsal side of the body, ...show more

Product details

  • Paperback | 60 pages
  • 189 x 246 x 3mm | 127g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236903021
  • 9781236903020