306 OF THE CIRCULATORY SYSTEM. SECT. XXIII. 2, 



convolutions, which precede the fecretory apertures 

 of the various glands and capillaries. 



In the veflels of the liver there is no intervention 

 of the heart; but the vena portarum, which does 

 the office of an artery, is diftended by the blood 

 poured into it from the mefenteric veins, and is by 

 this diftention ftimulated to contract itfelf, and propel 

 the blood to the mouths of the numerous glands, 

 which compofe that vifcus. 



II. The glandular fyftem of veffels may be di- 

 \ided into thofe, which take fome fluid from the 

 circulation ; and thofe, which give fomething to it. 

 Thofe, which take their fluid from the circulation are 

 the various glands, by which the tears, bile, urine, 

 perfpiration, and many other fecretions are produ- 

 ced ; thefe glands probably confift of a mouth to 

 felei, a belly to digeft, and an excretory aperture 

 to emit their appropriated fluids \ the blood is con- 

 veyed by the power of the heart and arteries to the 

 irjouths of thefe. glands, it is there taken up by the 

 living power of the gland, and carried forwards to 

 it? belly, and excretory aperture, where a part is fe- 

 parated, and the remainder abforbed by the veins for 

 further purpofes. 



Some of thefe glands are fqrnimed with long con- 

 voluted necks or tubes, as the feminal ones, which 

 are curioufly feen when injected with quickfilver. 

 Others feem to confift of fharter tubes, as that great 

 congeries of glands which conftitute the liver, and 

 thole of the kidneys Some have their excretory 

 apartures opening into refervoirs, as the urinary 

 and gall bladders. And others on the external body, 

 as thofe which fecrete the tears, and perfpirable 

 matter. 



Another great fyftem of glands, which have very 

 fhor t necks, are the capillary veiTels ; by which the 

 mienfibie perfpiration is fecreted on the fkin; and 



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the 



