ORGANS OF SENSE. 145 



aorta; ''', cut branches of the tenth pair to the pulmonic plexus; \ great 

 splanchnic nerve; ', lesser splanchnic nerve; *'°, solar or coeliac plexus; 

 ', semilunar ganglion of the right side ; ®, vagus of the right side ; ", do. of 

 the left side, with its numerous branches to the stomach ; ", supra-renal 

 plexus ; ", renal plexus ; '', branches to the intestinal canal ; ", aorti<3 

 plexus; '*, plexus to the seminal organs; '^''\ two lumbar ganglions, and 

 their connexion with the lumbar nerves and the aortic plexus; "'", two 

 sacral ganglions, connected with each other, and with the sacral nerves,., so 

 as to form plexuses about the pelvic vessels ; ", sacral plexus of the spinal 

 nerves. 



V. ORGANS OF SENSE. 



The organs of the senses establish certain relations between man and the 

 external world, by which he obtains all his knowledge of the physical 

 character and of the general and special properties of all surrounding 

 objects. The organs of sense are all symmetrical, and are usually coa- 

 sidered as five in number : the nose, or organ of smell ; the tongue, or organ 

 of taste ; the ear, or organ of hearing ; the eye, or organ of sight ; together 

 with the integuments, or the organ of touch. Each organ of sense is placed 

 near the surface of the body, is furnished with an appropriate apparatus 

 suited to its particular functions, and is in direct connexion with the nervous 

 centres. The four first mentioned organs are connected with particular 

 parts of the brain, each by its proper nerve. The sense of touch, how- 

 ever, is distributed over the whole surface of the body, and its apparatus 

 being supplied by the posterior or ganglionic roots of the fifth cerebral and 

 all the spinal nerves, is therefore connected with the cerebro-spinal axis 

 generally. 



1. Anatomy of the Integuments. 



The seat of the sense of touch, by means of which we become cognisant 

 of such peculiarities of matter as temperature, shape, weight, density, &c., 

 resides essentially in the skin proper, although existing to a considerable 

 degree in the mucous membranes. Those which are continuous with the 

 skin share with it in the peculiarities of its anatomy, both consisting of two 

 lamina, one external or superficial, named cuticle, epidermis, or epitheliunn, 

 the other deeper, and known as the cutis vera or chorion. Beneath the 

 latter is more or less of areolar or cellular and adipose tissue, which serves 

 to support and conduct the numerous vessels and nerves that supply this 

 highly organized structure. 



All parts of the skin, and, indeed, most structures in the body, possess a 

 certain degree of sensibility to temperature and to contact, that is, they 

 possess toiich generally ; but the power of discerning the other qualities of 



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