THE PITUITARY BODY. 243 and to return to it when moved by the attendants. Should hemiplegia occur, it indicates that the lesion exerts pressureeffects upon the pyramidal tracts, either in the crus, pons, or medulla. Irregularity of the heart's action, which is sometimes observed in connection with a cerebellar lesion, indicates a pressure upon the cardio-inhibitory center of the medulla. Abnormal mental symptoms are generally absent in connection with cerebellar lesions. When atrophy of the organ is present, or when other parts of the brain are diseased simultaneously with the cerebellum, mental derangements may be observed. When the middle crura of the cerebellum (those going to the pons) are affected by lesions which create irritation, rotary movements of the body and a lateral deflection of the head and eyes may be developed. As a rule, these rotary movements are toward the healthy side; but this is not invariably the case, as they sometimes are toward the side upon which the lesion is situated. It is a curious fact that most of the effects of cerebellar lesions are attributable to a greater or less extent to irritation of the crura. Lesions of the superior peduncle of the cerebellum are liable to induce paralysis of the motor-oculi nerve, as shown by the development of ptosis, external strabismus, and dilatation of the pupil. Hemianæsthesia and more or less ataxia may be induced by pressure upon the tegmentum and the fillet tract (lemniscus). THE PITUITARY BODY. That portion of the brain which lies in the sella turcica of the sphenoid bone is called the pituitary body or the hypophysis cerebri. It was formerly called the pituitary gland, because it was supposed to discharge "pituita" into the nostrils. It is diagrammatically shown in Fig. 37. It is a small, reddish mass, which consists of two lobes, of which the anterior is the larger and embraces the posterior. The anterior lobe is darker in color than the posterior, and, in the adult, consists of a large number of slightly convoluted tubules or alveoli, which are lined with epithelium. Sometimes a colloid substance is found within them. It is joined to the posterior lobes in mammals only. The posterior lobe is developed as a hollow projection from the portion of the cavity of the embryonic brain which is destined to constitute the cavity of the third ventricle. It remains small and undeveloped in the higher vertebrates but becomes transformed into an integral part of the brain in the lower vertebrates through the formation of nerve cells and nerve fibers within it. Occasionally, the cavity which originally existed in its substance remains unobliterated. The function of the pituitary body is unknown. In its microscopic structure, the anterior lobe closely resembles that of the thyroid body. THE MEDULLA OBLONGATA AND PONS VAROLII. The medulla oblongata is received anteriorly (ventrad) into a groove on the basilar process of the occipital bone, and posteriorly (dorsad) into a fossa between the cerebellar hemispheres. From its sides, the seventh, eighth, ninth, tenth, eleventh, and twelfth cranial nerves escape. Its form has been compared to an "irregularly truncated cone." It is expanded both laterally and antero-posteriorly at its upper portion, and measures about one inch in length, three quarters of an inch in its greatest breadth, and slightly less in its dorso-ventral plane. The anterior median fissure of the spinal cord is prolonged upward (cephalad) throughout the whole extent of the medulla, and terminates (at the junction of the medulla with the pons Varolii) in a deep recess, called the "foramen cæcum of Vicq d'Azyr." Some of the decussating bundles of the pyramids partially interrupt this fissure. The posterior median fissure of the spinal cord is also THE MEDULLA OBLONGATA AND PONS. 245 continued upward (cephalad) into the medulla, as far as the lower angle of the fourth ventricle, where the so-called "restiform bodies" diverge. We owe to Stilling, Van der Kolk, Türck, Meynert, Clarke, Flechsig, Krause, Spitzka, Laura, Aeby, Roller, Starr, and others who have devoted special study to the architecture of the medulla, the limited knowledge of this complicated piece of mechanism we now possess. Within this ganglion we find numerous collections of gray matter in addition to well-defined nerve tracts. Some of these gray masses are analogous to, and probably direct continuations of, distinct areas of the spinal gray substance. On the other hand, we are forced to admit the existence of other nodal masses, which are structurally independent of any relationship to the cord. Some well-defined tracts of nerve fibers within the cerebrum and spinal cord find their end in the gray masses of the medulla and pons; while other 1 In connection with the gray substance of the pons, the late researches of Flechsig have shed some light upon the relative development of different nerve tracts, and in this way helped to interpret some points in dispute respecting their distribution. This author draws the following conclusions : 1. A tract of nerve fibers passes from the frontal lobe of the cerebrum, through the anterior division of the internal capsule, and the inner two fifths of the crus cerebri, to the gray nuclei in the antero-median gray matter of the 204 LEVEILLE et E.SALLE. FIG. 50.-Anterior view of the medulla oblongata. (Sappey.) 1, infundibulum; 2, tuber cinereum; 3, corpora albicantia; 4, cerebral peduncle; 5, tuber annulare; 6, origin of the middle peduncle of the cerebellum; 7, anterior pyramids of the medulla oblongata; 8, decussation of the anterior pyramids; 9, olivary bodies; 10, restiform bodies; 11, arciform fibers; 12, upper extremity of the spinal cord; 13, ligamentum denticulatum; 14, 14, dura mater of the cord; 15, optic tracts; 16, chiasm of the optic nerves; 17, motor oculi communis; 18, patheticus; 19, fifth nerve; 26, motor cculi externus; 21, facial nerve; 22, auditory nerve; 23, nerve of Wrisberg; 24, glosso-pharyngeal nerve; 25, pneumogastric; 26, 26, spinal accessory; 27, sublingual nerve; 28, 29, 30, cervical nerves. nerve tracts begin in these gray masses and are either prolonged to other parts of the brain, or leave the substance of the medulla as cranial nerves, possessing various functions. The term "medulla oblongata," as first employed by Vieussens and Willis, included both the crura cerebri and the pons Varolii, in addition to the ganglion, to which the term is now restricted by more modern authors. It is used here to include only the collection of nerve tracts and gray masses situated between the pons and the spinal cord. The medulla has been subdivided by Krause into three portions, whose limits are as follows: The inferior portion extends from the plane of the first cervical nerve to the lower border of the olive; the middle portion includes that portion of the medulla between the upper and lower borders of the olive; the superior portion extends from the upper border of the olive to the plane intersecting the middle of the floor of the fourth ventricle. Sections of the inferior and middle portions exhibit the central canal more or less modified, and those of the superior portion show the ventricular floor. The line of origin of the anterior roots of the spinal nerves is not marked by a distinct furrow in the spinal cord; but in the medulla a well-marked longitudinal groove (which extends as far as the lower border of the pons) indicates the direct continuation of that line. This groove is partially obliterated pons. This tract of fibers is apparently prolonged (after traversing this gray mass) to the lateral and posterior portions of the cerebellum; hence, the gray substance of the pons must be regarded as interpolated in a tract which serves to unite the cerebellum with the frontal lobes chiefly, but not exclusively, of the opposed cerebral hemisphere. 2. The postero-median nuclei of the gray substance of the pons is similarly connected with a tract of fibers that joins the cerebellum with the cortex of the temporo-occipital region of the cerebrum. It never develops when the cerebellum is wanting, and is not clothed with myeline until some months after birth. The course of this tract seems to be (1) through the external one fifth of the crus; (2) through the internal capsule; (3) along the base of the lenticular nucleus of the corpus striatum; and, (4) outward to the cortex. The late development of these fibers apparently disproves any connection between them and the sense of hearing or of the tactile sense. 3. The caudate and lenticular nuclei of the corpus striatum are connected with the nuclei of the gray substance of the pons by means of fibers that pass downward through the median bundles of the crus to the substantia nigra and the nuclei of the pons. The fibers of this tract are connected with the cerebellum, after traversing these gray masses. MEDULLA GRAY MATTER OF MEDULLA OBLONGATA. 247 below the olivary body by transverse fibers; above this point it separates the olivary body from the pyramid. Out of this groove the roots of the hypoglossal nerve leave the substance of the medulla; they may therefore be considered as analogous to the anterior roots of the spinal nerves below. This analogy apparently holds good in respect also to the area of gray substance within the medulla from which the roots of this nerve appear to spring; although Spitzka is led to believe that the gelatinous substance anterior to the central canal of the spinal cord is more directly connected with its formation. The line of attachment of the posterior or sensory roots of the spinal cord is prolonged upon the surface of the medulla as a series of bundles which help to form the spinal accessory nerve. These are seen to approach the posterior roots of the spinal nerves in the cervical region, and to swing into a direct line of continuation with them above the level of the foramen magnum. At a higher level of the medulla the vagus nerve roots spring from the same line, and still higher up the roots of the glosso-pharyngeal nerve. Assuming, therefore, that these nerves escape from regions in the medulla that are analogous to those associated in the cord with the posterior roots of the spinal nerves, we are naturally led to infer that the fibers of origin of these nerves are probably connected with masses of gray substance within the medulla which are structurally related to the posterior horns of the spinal gray matter. This is apparently the fact, as subsequent pages will help to demonstrate. The changes which occur during the transition state (in which the spinal cord is so altered in its construction as to accommodate itself to the requirements of the medulla) may be simplified to the mind of some readers by an illustration employed by Quain, which I quote. He says: "The opening up of the central canal and separation of the lips of the posterior median fissure bring the gray matter to the surface of the fourth ventricle, while the posterior cornua are coincidently shifted to the side, much in the same way as it would |