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112 SCIENCE PRIMERS. [§ Vll. 



blood-vessels, and being packed close together with 

 connective tissue, make up the soft body we are 

 speaking of. This bo4y is in fact a gland, and 

 is called a salivary gland ; as you see it is not a 

 simple gland like a sweat gland, but is made up of a 

 host of tube-like glands all joined together, and 

 hence is called a compound gland. Being placed 

 far away from the mouth, it has to be connected with 

 the cavity of the mouth by a long tube, which is 

 called its duct. You cannot fail to notice how like 

 such a gland is, in its structure, to a lung. The lung 

 is in fact a gland secreting carbonic acid : and the 

 duct of the two lungs is called the trachea. The 

 salivary gland beneath the ear is called the parotid 

 gland ; there is another very similar one underneath 

 the corner of the jaw on either side, called the 

 submaxillary gland. By each of them a watery 

 fluid is secreted, which, flowing along their ducts 

 into the mouth and being there mixed with the 

 moisture secreted by the other glands in the mouth, 

 is called saliva. 



In the cavity of the abdomen lying just below the 

 stomach is a much larger but altogether similar com- 

 pound gland called the pancreas, which pours its 

 secretion called pancreatic juice into the alimentary 

 canal just where the small intestine begins (Fig. 17,^.) 



That large organ the liver, though the plan of its 

 construction is not quite the same as that of the pan- 

 creas or salivary glands, as you will by and by learn, 

 is nevertheless a huge gland, secreting from the blood 

 capillaries into which the portal vein (see p. 62) breaks 

 up, a fluid called bile or gall, which by a duct, the 

 gall duct, is poured into the top of the intestine (Fig. 



