46 OF SECRETION. 



68. SECRRTION is the production of certain /if/itids which resem- 

 ble the scrum in nothiity, and which are alto formed at the expense 

 oj the blood. 



69. Tears, saliva, bile, urine, &c., are liquids, secreted in this 

 way. 



70. The phenomenon of secretion always takes place in parti- 

 cular organs. Sometimes it is seated in the follicles, and some- 

 times in the glands. 



71. The fiMulrx are very small pouches which are strewed 

 through substance of the membranes, and which open upon their 

 surface, by small pores. 



72. The fuilidf* of the skin secrete the sweat ; those on the 

 edge of the eye-lids which secrete the yellow matter which some- 

 times accumulates during sleep, are organs of this kind. 



73. The (/lands are more voluminous organs, composed of small 

 granulations united in a compact and distinct mass. These granu- 

 lations are the seat of secretion, and they generally communicate 

 externally, by small tubes or conduits, which, uniting together 

 like the roots of a tree, finally form an excretory canal by which 

 the secreted liquid is poured out. 



74. The salivary glands which secrete the saliva, the lachrymal 

 glands, which secrete the tears, and the liver which secretes the 

 bile, are organs of this class. 



75. The act of secretion is not designed simply to produce liquids 

 useful in the exercise of certain functions, such as the saliva and 

 bile ; but also to free the blood from the old materials, separated 

 from the tissue of the organs by the act of nutrition, and other 

 useless or injurious matters, which may become mixed with it by 

 the effect of absorption. The secretion of urine, which takes 

 place in the kidneys, (situated in the abdomen, one on each side 

 of the spine) and the expulsion 'of it which follows, is the 

 principal means by which this sort of purification of the blood is 

 effected. 



63. What is secretion? 



69. Give examples of the secretions ? 



70. In what part does the secretion take place ? 



71. What are follicles? 



72. How is the sweat produced ? 



73. What are glands ? How do they communicate externally ? 



74. Give examples of s creting glands ? 



75. What a-e the objects of secretion? What organs secrete the urine ? 



