16 ANATOMY AND PHYSIOLOGY. 



motion of the intestines, through its various windings, and the 

 nourishing parts of it all absorbed by the lacteals, and by them 

 conveyed into the blood. These vessels are arranged in countless 

 multitudes along the sides of the winding passage they are so 

 framed as to admit the nutrimental parts, and reject the gross and 

 useless parts. The bowels are about twenty-five feet long, lined 

 with a soft mucus, and having valves to prevent the aliment from 

 returning back to the stomach ; the substance of the bowels, though 

 thin to a delicacy, is very strong; the skin of an ox-gut is said to 

 bear ihe blows of a gold-beater's hammer for years. 



BLOOD. 



The chyle, drawn off by all the secretory orifices, is carried along 

 millions of the finest ducts, and lodged in several commodious 

 glands from whence it is conveyed to a common receptacle, and 

 mounts through a perpendicular tube, called the thoracic duct. As 

 this is the principal nourishment of the whole system, its convey- 

 ance is guarded with peculiar caution. The tube not having 

 sufficient force of its own is laid contiguous to the great artery, 

 whose strong pulsation drives on the creeping fluid, enables it to 

 overcome the steep ascent, and unload its precious treasure at the 

 very door of the heart. Here it enters a large vein called the left 

 subclavian, most conveniently -opened for its reception in an 

 oblique manner, by which the refluent blood, assisted by a valve, 

 expedites instead of obstructing its passage. This milk, this 

 manna of nature, must be very acceptable to the blood, which has 

 now been supplying every gland in the system, and further im- 

 poverished by supplying myriads of vessels with matter for insen- 

 sible perspiration, yet, though, thus kindly recruited, it is not 

 refined. In its present state it is unqualified to perform the vital 

 tour; therefore, by a grand apparatus of muscular fibres, it is 

 wafted into the lungs, and pouring a thousand rills into either lobe 

 in the -spongy cells of their amazing laboratory, it imbibes the in- 

 fluences of the external air, giving out some useless parts, and 

 imbibing some more necessary, and thus its heterogeneous parts are 

 thoroughly incorporated. Here its red color commences, from the 

 change it undergoes from the action of the air ; and its whole sub- 

 stance is rendered cool, smooth, and florid. Thus improved it is 

 transmitted to the left ventricle of the heart, a strong, active, 

 unceasing muscle, placed in the centre of the system. 3 ^ Impelled 



* This wonderful machine will go night and day for eighty years together, at the 



