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; 
7, 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; ™, aortic 
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 con- 
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. Hach 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 
lamine, one external or superficial, named cuticle, epidermis, or epithelium, 
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 detects to temperature and to contact, that is, they 
possess touch generally ; but the power of discerning the other qualities of 
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