ANDRONOMY. 409 



are necess try to the preservation of life, in sleep as well as in a con- 

 scious state. The ganglionic system, is, in fact, a collection of fila- 

 ments, from every nerve in the body, meeting in the ganglia, and 

 causing every part of the system to be affected by, or sympathize 

 with, every other part ; while the mind takes cognizance of the state 

 of the body, or is prompted to action, by the sensations thus ex- 

 perienced. Hence the ganglionic system has been termed the great 

 sympathetic nerve. 



Of the eye, as the organ of sight, we have already spoken in treat- 

 ing of Optics, (p. 361). The internal ear, is hollowed out from the 

 side of the skull ; and the membrane of the tympanum, is stretched 

 over the passage leading to this cavity ; within which are four small 

 bones, serving to transmit the vibrations of the air, from the mem- 

 brane to the labyrinth, or innermost spiral chamber, whence the 

 auditory nerve conveys the impression to the brain. The sense of 

 smelling, depends on the olfactory nerves ; that of tasting, on the 

 nerves of the tongue, terminating in small papillae or pointed protu- 

 berances ; and the sense of feeling, is produced by nervous papillae 

 extending nearly to the surface of the skin. The skin, consists of 

 the cuticle, epidermis, or scarf skin, on the exterior; the rete muco- 

 sum, in which the nerves terminate, and which gives the color or 

 complexion ; and the dermis, or true skin, which is thicker than the 

 other layers, and is connected with the cellular membrane covering 

 the muscles of the body. 



4. Jlngiology, is that division of Anatomy which treats of the 

 vessels, of the human body ; that is the blood vessels, lacteals, and 

 absorbents. The blood vessels, are the heart, arteries, and veins ; 

 with which the lungs are so closely connected, that we shall here 

 describe them together. The heart and lungs occupy the thorax, or 

 chest ; and are separated from the lower viscera by a membranous 

 partition, called the diaphragm. The heart, formed by thick and 

 strong muscular coatings, contains two cavities, called the right, and 

 the left ventricle, acting as forcing pumps ; below which are two 

 other cavities, called the right and left auricle, of inferior strength. 

 The blood, whose use is to nourish the body, is collected from all 

 parts of the same, by the veins, and enters through the superior and 

 the inferior vena cava, into the right auricle of the heart. From 

 this it passes into the right ventricle, through an aperture with a 

 valve, which does not allow it to return. This ventricle, then con- 

 tracting, drives the blood, through the pulmonary artery, into the 

 lungs ; whence, after being acted upon by the air, it proceeds, through 

 the pulmonary veins, into the left auricle, and from thence into the 

 left ventricle of the heart, which also has a valve to prevent its turning 

 back, in its course. This ventricle, then contracting, acts as another 

 forcing pump, to drive out the blood, through the aorta, or systemic 

 artery, and its numerous branches, to every part of the system. 



Thus, by the alternate contraction and relaxation of the ventricles, 

 the double circulation of the blood is maintained, first through the 

 lungs, and then through the body. The arteries, are more deeply 

 seated than the veins ; as any accident rupturing them would be more 

 suddenly fatal : for the external veins, receiving the blood through 

 52 2 M 



