Mental Diseases and Their Modern Treatment | Page 3

but it performs the work of holding together vast numbers of small arteries and veins that carry on, to a large extent, the circulation of the brain. This membrane is adherent to the brain surfaces, covering closely the convolutions and dipping into the sulci or spaces between them. As the blood vessels pass into the brain from the pia mater like so many little rootlets, the membrane is of course fastened snugly to that organ.
The brain itself is divided into hemispheres. These hemispheres are subdivided into lobes. The hemispheres are separated by the great longitudinal fissure which extends throughout the length of the cerebrum in the middle line, reaching down to the base of the brain in front and behind, but interrupted in the middle by a broad band of white matter termed the corpus callosum. This band unites the hemispheres like the firm mass which united the Siamese twins.
Each half of the brain is divided into what are called the frontal, parietal, occipital and temporal lobes; and for a fifth lobe we have what is termed the Island of Reil.
After removing the coverings we come to the convolutions. These are separated from each other by depressions called sulci. It is supposed that the deeper the sulci, the greater the brain power. This is not always true, but the deeper the sulci the greater the opportunity for a deposit of gray matter.
Upon the outer surfaces of the convolutions, and on the sides and bottom of the sulci, is a gray matter called the cortical substance. In the gray matter there are five or six layers of nerve cells. Many of these cells are shaped like a pyramid, while some are round and some are elongated. The nerve cells have a nucleus, a plasma, and a surrounding pellicle or skin, and also outreaching tentacles or arms. The entire outfit is called the neuron. Within the cortical substance we find the white fibers which are in reality the connecting wires of communication between the nerve extremities of the body and the neurine batteries of the brain. The nerve fibers convey impressions to the cells, and the cells which receive these impressions act according to the impression which is made.
Besides nerve cells and nerve fibers there is a substance in the brain called the neuroglia. The neuroglia "is a transparent, nucleated, homogeneous, non-fibrillated matrix, somewhat resembling the fibrillated connective tissue of the spinal cord." Supposing you were to put a lot of berries on some strings, and then put them into a glass jar with the ends of the strings hanging over the mouth of the jar, and then fill in the interstices with some syrup, this syrup might represent or typify the neuroglia. After the Almighty had constructed the nerve cells which are the homes and centers of mental activity, and after He had connected them by nerve fibers with the great organs and surfaces of the body, that is, with the external world, He filled up the cracks with neuroglia, which is simply connective tissue, and other supporting material.
Histologically, you will remember that the cerebral mass is composed of gray matter filled with cells of many kinds, of white matter (that is, white nerve lines of communication), and of neuroglia, which is a nucleated mass thrown in for the support of the rest of the brain.
Having plodded through the brain, we arrive at the base, and, as we expose it to view, we see the longitudinal fissure, the corpus callosum, and its peduncles, the lamina cinerea, the olfactory nerve, the fissure of Sylvius, the anterior perforated space, the optic commissure, the tuber cinereum, the infundibulum, the pituitary body (which is said to be the seat of the soul), the corpora albicantia, the posterior perforated space, and the crura cerebri. Now I trust that you will never forget any of these since I have taken the trouble to bring them to your notice.
From the base of the brain are given off twelve pairs of nerves. These are called nerves of sensation, motion, and special sense, and are the mediums through which impressions, both external and internal, are conveyed to the brain, and through these all orders of the mind to the body are conveyed for execution.
The functions of seeing, smelling, tasting and hearing, are performed by the optic, olfactory, trifacial, and glossopharyngeal nerves. Portions of those just named, and the remainder of the twelve, constitute the nerves of sensation and motion. Some anatomists name but nine pairs of nerves. We prefer a division of twelve, and shall enumerate them as follows:
1. Olfactory, 2. Optic, 3. Motor oculi, 4. Pathetic, 5. Trifacial, 6. Abducens, 7. Facial, 8. Auditory, 9. Glosso--pharyngeal, 10. Pneumogastric, 11. Spinal accessory, 12. Hypoglossal.
There are in the brain five ventricles. The chief of these are the lateral, and those of