into action without the necessity of the interference of the mind. Though to a certain extent they may be under the influence of the will, yet it is only in a secondary degree. No one can long suspend the movements of respiration;* for in a short time, instinctive feeling issues its irresistible mandate, which neither requires the aid of erring wisdom, nor brooks the capricious interference of the will.

786. The fourth, seventh, and tenth pairs of nerves, (7, 8, 9, fig. 132,) with the spinal accessory, phrenic, and external respiratory, are not only connected with the function of respi ration, but contribute to the expression of the passions and emotions of the mind.

787. The influence of this order of nerves in the expres sion of the passions, is strikingly depicted in Sir Charles Bell's Treatise on the Nervous System. "In terror," he remarks, "we can readily conceive why a man stands with his eyes intently fixed on the object of his fears-the eyebrows elevated, and the eyeballs largely uncovered; or why, with hesitating and bewildered steps, his eyes are rapidly and wildly in search of something. In this way, we only perceive the intense application of his mind to the objects of his appre hension, and its direct influence on the outward organs."

788. But when we observe him further, there is a spasm in his breast; he cannot breathe freely; the chest remains elevated, and his respiration is short and rapid. There is a

* Dr. Elliotson, and some other writers on physiology, have detailed cases of death from voluntary suspension of respiration. But these cases are not conclusive, as examinations were not made, so as to determine positively, that death did not result from disease of the heart, brain, or some other vital organ.

Can respiration be suspended for any considerable length of time? 786. What nerves contribute to the expression of the passions and emotions of the mind? 787, 788. What does Sir Charles Bell say of the influence of this order of nerves in the expression of the passions?

gasping and convulsive motion of his lips, a tremor on his hollow cheeks, a gasping and catching of his throat; his heart knocks at his ribs, while yet there is no force in the circulation - the lips and cheeks being ashy pale."

789. "These nerves are the instruments of expression, from the smile upon the infant's cheek, to the last agony of life. It is when the strong man is subdued by this mysterious influence of soul on body, and when the passions may be truly said to tear the heart, that we have the most afflicting picture of human frailty, and the most unequivocal proof that it is the order of functions we have been considering, that is thus affected. In the first struggle of the infant to draw breath, in the man recovering from a state of suffocation, and in the agony of passion, when the breast labors from the influence at the heart, the same system of parts is affected, the same nerves, the same muscles, and the symptoms or character have a strict resemblance."

790. The seventh pair of nerves not only communicates the purposes of the will to the muscles of the face, but at the same time it calls them into action, under the influence of instinct and sympathy. On this subject a late writer remarks, "How expressive is the face of man! How clearly it announces the thoughts and sentiments of the mind! How well depicted are the passions on his countenance! tumultuous rage, abject fear, devoted love, envy, hatred, grief, and every other emotion, in all their shades and diversities, are imprinted there, in characters so clear that he that runs may read! How difficult, nay, how impossible, is it to hide or falsify the expressions which indicate the internal feelings! Thus conscious guilt shrinks from detection, innocence declares its confidence, and hope anticipates with bright expectation.' Observation. The fifth pair of nerves (fig. 126) is dis

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789. Are they also the instruments of expression, either of joy or grief? 790. What is said in reference to the seventh pair of nerves? Where is the fifth pair of nerves distributed?

tributed to the parts of the face on which the seventh pair ramifies. The former serves for sensation, the latter for motion. Thus, when the seventh pair of nerves is divided, or its functions destroyed by disease, the side affected loses all power of expression, though sensation remains unaffected. On the contrary, if we divide the fifth pair, sensation is entirely destroyed, while expression remains.

791. 5th. The sympathetic nerve. This nerve confers vitality on all the important portions of the system. It exerts a controlling influence over the involuntary functions of digestion, absorption, secretion, circulation, and nutrition. Every por tion of the body is, to a certain extent, under its influence, as filaments from this system of nerves accompany the bloodvessels throughout their course.

792. An important use of the sympathetic nerve is to form a communication of one part of the system with another, so that one organ can take cognizance of the condition of every other, and act accordingly. If, for example, disease seizes the brain, the stomach, by its sympathetic connection, knows it; and as nourishment would add to the disease, it refuses to receive food, and perhaps throws off what has already been taken. Loss of appetite in sickness is thus a kind provision of nature, to prevent our taking food when it would be injurious; and following this intimation, we, as a general rule, should abstain from food until the appetite returns.

Fig. 133. A back view of the brain and spinal cord. 1, The cerebrum. 2, The cerebellum. 3, The spinal cord. 4, Nerves of the face. 5, The brachial plexus of nerves. 6,7,8,9, Nerves of the arm. 10, Nerves that pass under the ribs. 11, The lumbar plexus of nerves. 12, The sacral plexus of nerves. 13, 14, 15, 16, Nerves of the lower limbs.

What is the function of this nerve? What is the effect if the seventh pair is divided, or its function destroyed by disease? 791. What is said of the sympathetic nerve? 792. What is the use of the sympathetic system? Explain fig. 133.

Note. Let the anatomy and physiology of the nervous system be reviewed from figs. 131, 132, 133, or from anatomical outline plate, No. 8.