great irregularity of the cranial nerves. He argued that if the endowment of a nerve depend on the relation of its roots to the columns of the spinal marrow and the base of the brain, then the observation of their roots must indicate to us their true distinction and their different uses. It was necessary to know in the first place whether the phenomena exhibited on injuring the separate roots of the spinal nerves correspond with what was suggested by their anatomy. He hesitated to put the question to the test of experiment because of the cruelty that seemed necessarily involved. It finally occurred to him, however, that it was best to experiment on an animal in a state of insensibility, as otherwise it might be difficult to distinguish between the expression of pain and the effect produced through the motor

nerves.

"I therefore," he continues, "struck a rabbit behind the ear, so as to deprive it of sensibility by the concussion, and then exposed the spinal marrow. On irritating the posterior roots of the nerve, I could perceive no motion consequent, on any part of the muscular frame; but on irritating the anterior roots of the nerve, at each touch of the forceps there was a corresponding motion of the muscles to which the nerve was distributed. These experiments satisfied me that the different roots and the different columns from whence these roots arose, were devoted

to distinct offices, and that the notions drawn from the anatomy were correct." In a paper communicated to the Royal Society of London in 1821, we find Sir Charles Bell pursuing a similar line of argument and reporting a similar method of investigation in reference to the function of one of the cranial nerves. He drew attention to the complicated nerve supply of the face, inexplicable on the assumption that the nerves are confined to a single function. He maintained that an organ that has only one function has only one nerve, and assumed that the presence of a number of nerves supplying the same part of the body gave ground for surmising a variety of function. He submitted to special examination the facial nerve (portio dura), the branches of which are so largely concerned in the expression of the emotions, and the paralysis of which gives rise to what is now known as Bell's palsy. He produced artificial paralysis in experimental animals by dividing the nerve after its emergence from the stylo-mastoid foramen. The cutting of the nerve called forth no sign of pain. The muscles of the side of the face on which the nerve was cut no longer acted in harmony with the other muscles involved in the act of respiration, and in the expression of emotion so closely associated with respiratory movements. If the facial nerve of one side of the face is cut and that of the other left intact and the animal is bled to death, the

contrast in expression between the two sides of the face of the dying animal is most striking.

The different functions of the nerves afford a clue to the functions of the brain and spinal cord. Some of the nerve trunks are made up of filaments that merely convey sensations; while other nerve trunks are made up of filaments that merely convey motor impressions to the muscles: a third class of nerve trunks are made up of the two kinds of filaments, as we have seen in the case of the spinal nerves. The brain and cord in turn are divided into parts concerned respectively with sensations and bodily movements. By many authorities in physiology Bell's contribution to neurology has been compared in value with Harvey's discovery of the circulation of the blood. As early as November 26, 1807, Bell had written to his brother: "I have done a more interesting nova anatomia cerebri humani than it is possible to conceive. I lectured it yesterday. I prosecuted it last night till one o'clock; and I am sure it will be well received."

François Magendie, who founded the "Journal de physiologie expérimentale" in 1821, confirmed in the following year, by experiments on a litter of eight puppies six weeks old, the results obtained by Sir Charles Bell in reference to the functions of the roots of the spinal nerves. At that time Magendie had not heard of Bell's experiments to determine