238 



COLLEGE ZOOLOGY 



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to stop, since a secretion from glands opening near the jaws tends 



to prevent coagulation. Blood is 

 sucked up by the dilation of the mus- 

 cular pharynx (Fig. 170, 2). The short 

 oesophagus leads from the pharynx 

 into the crop, which has eleven pairs 

 of lateral branches (j, 4). Here the 

 blood is stored until digested in the 

 small globular stomach (5). A leech 

 is able to ingest three times its own 

 IZ weight in blood, and, since it may 

 take as long as nine months to digest 

 this amount, meals are few and far 

 between. The intestine (6) leads 

 directly to the anus (7). 



The absorbed food passes into the 

 blood-vessels (Fig. 170, //) and the 

 ccdomic cavities, and is carried to all 

 parts of the body. The ccelom is 

 usually small because of the develop- 

 ment of a peculiar kind of connective 

 tissue known as botryoidal tissue. The 

 spaces in the body which are not filled 

 up by this tissue are called sinuses, 

 and in many species contain a fluid 

 very much like true blood. 



Respiration is carried on at the 

 surface of the body, oxygen being 

 taken into and carbon dioxide given 

 7 jQk Zf& off by many blood capillaries in the 



FIG. 170. View of the internal organs of the leech, Birudo medicinalis. 

 I, head with eye-spots; 2, muscular pharynx; 3, ist diverticulum of crop; 

 4, nth diverticulum of crop; 5, stomach; 6, rectum; 7, anus; 8, cerebral 

 ganglia; Q, ventral nerve-cord; 10, nephridium; n, lateral blood-vessel; 

 12, testis; 13, vas deferens; 14, prostate gland; 15, penis; 16, ovary; 17, uterus. 

 (From Shipley and MacBride.) 



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