. A manual of elementary zoology . Zoology. the crayfish 257 fill like that of the frog, which is a separate part of the ccelom. A blood-vascular system in which, as in the crayfish, the blood on leaving the arteries bathes the organs of the body is said to be open. One in which, as in the worm and the frog, it is carried through the organs in capillaries which lead direct to veins is said to be closed. The blood of the crayfish is a clear fluid, which contains white corpuscles and clots readily—an obvious advantage to an animal whose open vascular system causes it to bleed freely from any wou
. A manual of elementary zoology . Zoology. the crayfish 257 fill like that of the frog, which is a separate part of the ccelom. A blood-vascular system in which, as in the crayfish, the blood on leaving the arteries bathes the organs of the body is said to be open. One in which, as in the worm and the frog, it is carried through the organs in capillaries which lead direct to veins is said to be closed. The blood of the crayfish is a clear fluid, which contains white corpuscles and clots readily—an obvious advantage to an animal whose open vascular system causes it to bleed freely from any wound. An organic compound of copper, known as hcemocyanin, which is dissolved in it, plays the same part as haemoglobin, taking up oxygen in the respiratory organs and parting with it to the tissues. In the oxidised condition it is of a blue colour and tinges the blood. The respiratory apparatus of the crayfish is con- 2?!anfry tained in the gill- chambers. The gills are branched, thin-walled struc- tures, standing upon the coxo- podites of the thoracic limbs and the inner wall of the gill-chamber. In them the blood circulates and exchanges its carbon dioxide for the oxygen which is dissolved in the water that is kept flowing through the chamber by the action of the second maxilla.' This limb is held firm by the curved end of its endopodite, which fits into a groove upon the mandible at the base of the palp, while the exopodite or scaphognathite, flapping at the rate of sixty strokes a minute, bales water forwards, out of the gill-chamber and under the opening upon the antenna of the green gland, whose excreta it thus sweeps away with the foul water from the gills. By this action fresh water is drawn into the chamber between the bases of the legs. No doubt the blood. Fig. 164.—A podobranch of the crayfish, seen from be- hind. Base ; cf., coxopodite ; gill', lam., lamina; sb., setobranch or tuft of coxopoditic setas ; stm., Please note that these images are extracted fr
Size: 1212px × 2061px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjectzoology, bookyear1920
