Page:Observations on Man 1834.djvu/39

 phænomena by these laws. This is the method of analysis and synthesis recommended and followed by Sir Isaac Newton.

I shall not be able to execute, with any accuracy, what the reader might expect of this kind, in respect of the doctrines of vibrations and association, and their general laws, on account of the great intricacy, extensiveness, and novelty of the subject. However, I will attempt a sketch in the best manner I can, for the service of future inquirers.

Section I
THE DOCTRINE OF VIBRATIONS, AND ITS USE FOR EXPLAINING THE SENSATIONS.



the word brain, in these observations, I comprehend all that lies within the cavity of the skull, i.e. the cerebrum, or brain properly so called, the cerebellum, and the medulla oblongata.

This proposition seems to be sufficiently proved in the writings of physicians and anatomists; from the structure and functions of the several organs of the human body; from experiments on living animals; from the symptoms of diseases, and from dissections of morbid bodies. Sensibility, and the power of motion, seem to be conveyed to all the parts, in their natural state, from the brain and spinal marrow, along the nerves. These arise from the, not the part, every where, and are themselves of a white medullary substance. When the nerves of any part are cut, tied, or compressed in any considerable degree, the functions of that part are either entirely destroyed, or much impaired. When the spinal marrow is compressed by a dislocation of the vertebræ of the back, all the parts, whose nerves arise below the place of dislocation, become paralytic. When any considerable injury is done to the medullary substance of the brain, sensation, voluntary motion, memory, and intellect, are either entirely lost, or much impaired; and if the injury be very great, this extends immediately to the vital motions also, viz. to those of the heart, and organs of respiration, so as to occasion death. But this does not hold equally in respect of the cortical substance of the brain; perhaps not at all, unless as far as injuries done to it extend themselves to the medullary substance. In dissections after apoplexies, palsies, epilepsies, and other