The Nerves and Brain

The vast complexity of the human mind is such, however, that belief in psychiatry remains very largely a matter of personal opinion. The different schools maintain their own views and there are few objective ways of deciding among them. If further advance is to be made, it will come when the basic science of the nervous system (neurology) is sufficiently developed.

Neurology began with a Swiss physiologist, Albrecht von Haller (1708-77), who published an eight-volume textbook on human physiology in the 1760s. Before his time, it had been generally accepted that the nerves were hollow and carried a mysterious "spirit" or fluid, much as veins carried blood. Haller, however, discarded this and reinterpreted nerve action on the basis of experiment.

For instance, he recognized that muscles were "irritable"; that is, that a slight stimulus of a muscle would produce a sharp contraction. He also showed, however, that a slight stimulus to a nerve would produce a sharp contraction in the muscle to which it was attached. The nerve was the more irritable of the two and Haller judged that it was nervous stimulation rather than direct muscular stimulation that controlled the movements of muscles.

Haller also showed that tissues themselves do not experience a sensation but that the nerves channel and carry the impulses that produce the sensation. Furthermore, he showed that nerves all lead to the brain or the spinal cord, which are thus clearly indicated to be the centers of sense perception and responsive action. He experimented by stimulating or damaging various parts of the animal brain and then noting the type of action or paralysis that resulted.

Haller's work was carried further by the German physician, Franz Joseph Gall (1758-1828), who began lecturing on the subject in 1796. He showed that the nerves led not merely to the brain, but to the "gray matter" on the surface of the brain. The "white matter," below the surface, he held to be connective substance.

Like Haller, Gall felt that particular parts of the brain were in control of particular parts of the body. He carried this to extremes, feeling that specific parts of the brain were assigned not only to particular sense perceptions and to particular muscle movements, but also to all sorts of emotional and temperamental qualities. This view was carried to the point of absurdity by his later followers who felt that these qualities could be detected, when present in excess, by feeling bumps on the skull. Thus was developed the pseudoscience of "phrenology."

The silliness of phrenology obscured the fact that Gall was partly right and that the brain did indeed have specialized areas. This possibility was lifted out of pseudo- science and back to rational investigation by the French brain surgeon, Paul Broca. As a result of a number of post mortems, he showed, in 1861, that patients, suffering from a loss of the ability to speak, possessed damage to a certain specific spot on the upper division of the brain, the cerebrum. The spot was on the third convolution of the left frontal lobe which is still called "Broca's convolution."

By 1870, twoGerman neurologists, Gustav Theodor Fritsch (1838-91)andEduard Hitzig (1838-1907), had gone even further. They exposed the brain of a living dog and stimulated various portions with an electric needle. They found that the stimulation of a particular spot would induce a particular muscular movement and in this way, they could map the body, so to speak, on the brain. They were able to show that the left cerebral hemisphere controlled the right part of the body while the right cerebral hemisphere controlled the left.

Thus, there came to be no doubt that not only did the brain control the body, but that it did so in a highly specific way. It began to seem that there was at least a conceivable chance that all mental function could be related in one way or another to brain physiology. This would make the mind merely an extension of the body and threatened to bring man's highest powers within the mechanistic domain.

More fundamentally still, the cell theory, when it came into being, was eventually applied to the nervous system. The biologists of the mid-nineteenth century had detected nerve cells in the brain and spinal cord, but were vague as to the nature of the nerve fibers themselves. It was the German anatomist, Wilhelm von Waldeyer (1836-1921), who clarified the matter. He maintained, in 1891, that the fibers represented delicate extensions from the nerve cells and formed an integral part of them. The whole nervous system, therefore, consisted of "neurons"; that is, of nerve cells proper, plus their extensions. This is the "neuron theory." Furthermore, Waldeyer showed that extensions of different cells might approach closely but did not actually meet. The gaps between neurons later came to be called "synapses."

The neuron theory was placed on a firm footing through the work of the Italian cytologist, Camillo Golgi (1844-1926),andthe Spanish neurologist, Santiago Ramon y Cajal (1852-1934). In 1873, Golgi developed a cell stain consisting of silver salts. By use of this material, he revealed structures within the cell ("Golgi bodies") whose functions are still unknown.

Golgi applied his staining method to nerve tissue in particular and found it well adapted for the purpose. He was able to see details not visible before, to make out the fine processes of the nerve cells in unprecedented detail, and to show synapses clearly. Nevertheless, he opposed Waldeyer's neuron theory when that was announced.

Ramon y Cajal, however, upheld the neuron theory strongly. Using an improved version of the Golgi staining technique he demonstrated details that established the neuron theory beyond question and worked out the cellular structure of the brain and spinal cord, and of the retina of the eye, too.