Above all there rises the cerebrum or large brain, exceeding in size all the other contents of the skull. Above and in front of the medulla oblongata is a quantity of fibrous matter which from its shape and position has been called the "bridge" or pons varolii.Ĥ. ![]() Its precise functions are still much disputed, but it seems to play an important part in coordinating locomotive action.ģ. Higher up and projecting backwards over this into the lower part of the back of the skull is a large, laminated mass, forming the cerebellum. Hence the fatal nature of injuries in this quarter.Ģ. From it proceed the nerves of the face and those governing the actions of the heart and lungs. It is, in fact, the prolongation of the spinal cord. The medulla oblongata, which is situated at the root of the brain where the spinal cord widens out on entering the skull. The brain itself is divided into several portions or organs, the functions of which are, however, in many cases but obscurely apprehended. ( See illustrations at the beginning of the book. The entire surface of the body is thus connected with the brain through the spinal cord by an elaborate telegraph system. The strands of nerves dividing and subdividing as they proceed farther from the trunk branch out into the finest threads through all parts of the skin, so that it is practically impossible to prick any place even with the finest needle without injury to some nerve. The nerves coming from the back of the spine are called the afferent, or sensory nerves, because by their means the molecular movements which give rise to sensations, are conveyed inwards from the various organs of the body. The nerves proceeding from the front of the spinal column are called the anterior, efferent, or motor nerves, inasmuch as they are the channels employed in the transmission of impulses outwards, and are thus the instruments of muscular movement. The spinal cord consists of a column of white, fibrous matter, enclosing a core of grey, cellular substance.įrom the spinal cord, between every two vertebrae, there issue forth two pairs of nerves. ![]() The central mass, called the cerebro-spinal axis, is made up of the brain and the spinal cord passing from it down through the backbone. The cerebro-spinal system itself is also composed of two parts or subdivisions, the central mass and the branches which ramify throughout the body. ![]() Whilst the former controls organic or vegetative life, the latter constitutes the bodily machinery of our mental states. The nervous apparatus of the animal organism is two-fold - the sympathetic system, and the cerebro-spinal system. In describing the action of the senses later on, we will say a brief word on the physical and physiological conditions of each in particular, but a few very general remarks on the nature of the physical basis of conscious life as a whole may be suitable here. The nature of the external agencies which arouse sensation is the subject-matter of the science of Physics the character of the process within the organism which precedes or accompanies the psychical state is studied by the science of Physiology while the investigation of the conscious operation itself is the function of Psychology. Thereupon, a completely new phenomenon, the conscious sensation, is awakened. This consists of a molecular disturbance in the substance of the nerves which is propagated to the brain. This action, transmitted in some form of motion to the sense-organ, gives rise there to the second stage. First, there is an action of the physical world external to the organism. The excitation of a sensation usually comprises three stages. A being capable of sensations is described as sentient, or sensitive and the term sensuous may be applied to all those mental states which are acts, not of the soul alone, but of the animated organism.Įxcitation of Sensation. To evoke these particular groups of sensations are called sense-organs. The special portions of the organism endowed with the property of reacting to appropriate stimuli so as The power of experiencing sensations in general is termed sensibility, while the capacity of the living being for a particular species of sensations is called a sense. A sensation is thus a modification, not of the mind alone, nor of the body alone, but of the living being composed of mind and body. It may, however, be described as an elementary psychical state aroused in the animated organism by some exciting cause. Such being the case, sensation cannot, properly speaking, be defined. ![]() The most fundamental and primitive form of conscious life is sensation.
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