(16) Tremor on both sides; but strongest on the homonymous side. (18) Sight is perfect on both sides, C. Twenty-four hours after operating. (1a) Rotating the table in clockwise direction, i. e., toward the operated side, the frog moves his head in anti-clockwise direction; after rotating, the head is brought back beyond the sagittal axis of the body in clockwise direction. (Ib) Rotating in anti-clockwise direction elicits no head movements; but a slight, circular movement of the body in an anti-clockwise direction is noted after rotating the table. (5) Is increased by the slightest stimulation. D. Two days after operating, (a) Same as after one day but in addition, sometimes a circular movement of the body in clockwise direction after rotating the table. (b) Same as after one day. (5) Diminishing. E. Three days after operating, (2), (3), and (4) were temporarily normal during short intervals while the frog was resting. F. Five days after operating, (5) Frog rotates only when it attempts to jump. G. Six days after operating, (5) Frog, on jumping, sometimes lands on dorsum. H. Ten days after operating, (13) Is normal. (1), (1), (3), and (4) are still far from normal. (5) On jumping, frog sometimes lands on dorsum and sometimes on homonymous side. I. No appreciable change in any symptoms from tenth to fifteenth day. XVII. Unilateral excision of the right side of the medulla anterior to the origin of the vagus group. (a) The same phenomena as observed after operation XVI; excepting that (b) Abdominal respiration is intact on both sides. (c) The croak reflex is normal immediately after the operation. (d) The bilateral apnoeic pauses in abdominal respiration, after rotating movements around the sagittal axis, are pronounced. XVIII. Unilateral excision of the right side of the medulla posterior to the origin of the vagus group to the calamus scriptorius. Causes from first to fifteenth day (1) Slight impairment of the abdominal respiration on the homonymous side. (2) Contraction of pupil on the homonymous side. (3) Weakness of limbs on the homonymous side. (4) Position of legs, body and head as observed after operation XVI, but in a lesser degree. They improved during the first week but did not regain normal. XIX. Unilateral excision of the right middle third of the medulla including the origin of the vagus group. (a) Phenomena which showed no change from first to the fifteenth day(1) Abdominal respiration on the homonymous side is completely abolished. (2) Pupil of this side is contracted. (b) Phenomina as observed after operation XVIII, (1) Position of head, legs, and body. (2) Defect in locomotion. XX. Bilateral excision of the middle third of the medulla, including the origin of the vagus group. (a) Abdominal respiration is abolished on both sides, also, the croak, turnover, and swallowing reflex is gone. (b) The head points into the ground. (c) Urostylic prominence is gone. (d) Complete inversion of oesophagus and stomach with prolapsus outside of the mouth. (e) Heart becomes feeble two hours after operating. (f) Eight hours after operating, respiration of nares and mouth is exaggerated, due to asphyxia. (g) Frogs died 8 hours after operating. XXI. Excision of everything anterior to the spinal cord. (a) Respiratory, croak, swallowing, heart-action, and turn-over reflexes are gone entirely. (b) Sense of equilibrium is lost. (c) Eye reflex and sight is lost. (d) Stimuli are answered sooner and with greater certainty than when higher portions of the brain are intact. (e) Heart action gradually ebbs away during the five hours which the frog usually lives after the operation. XXII. Excision of everything anterior to and including the anterior portion of the spinal cord almost down to the origin of the brachial plexus. (a) All phenomena of operation XXI. (b) Co-ordinated movements fade away during the first two to three hours after this operation. (c) Three hours after operating, the fore limbs cannot support the body any more. (d) The frog is usually dead five hours after the operation. THE CENTRAL GUSTATORY PATHS IN THE BRAINS OF BONY FISHES. By C. JUDSON HERRICK. Studies from the Neurological Laboratory of Denison University. No. XVIII. SECTION II. THE PERIPHERAL GUSTATORY SYSTEM IN FISHES. SECTION III. THE CENTRAL GUSTATORY System of CYPRINOID FIShes. 1. Primary Gustatory Centers. 2. Secondary Gustatory Tracts. (1) Descending Secondary Gustatory Tract. (2) Ascending Secondary Gustatory Tract. 3. Superior Secondary Nucleus and its Connections. SECTION IV. THE CENTRAL GUSTATORY SYSTEM OF SILUROID FISHES. SECTION V. SUMMARY AND GENERAL CONCLUSIONS. Table of the Gustatory Paths in Fishes. Mammalian Homologies of the Gustatory Centers of Fishes. The conception of the nervous system as a mechanism for putting the organism into correspondence with the external environment and, in higher animals, for coordinating the reacting apparatus itself (internal environment) may be said to give the key to its evolutionary history. These two factors have given direction to the differentiation of the nervous system into somatic and visceral systems respectively and the further subdivision of each of these. This study was awarded the Cartwright Prize for 1905 by the Alumni Association of the College of Physicians and Surgeons, Columbia University, New York. It is published simultaneously in the Journal of Comparative Neurology and Psychology and the Bulletin of the Scientific Laboratories of Denison University, pages 375 to 456 of volume XV of the Journal being severally identical with pages 35 to 116 of volume XIII of the Bulletin. The labors of the students of nerve components have given us for the peripheral nervous system a paradigm or schema which seems to hold for all vertebrates, though with infinite variation in its details; and it now remains to correlate these peripheral components with the central conduction paths so as to give a detailed knowledge of the whole course of each reflex pathway. In attacking this general problem there are obviously two general lines of procedure open to us :-(1) beginning with the simplest brains we may work out exhaustively for each critical species in the phylogenetic series the conduction paths as completely as possible by monographic treatment of types and thus in the end approximate to a reconstruction of the phyletic history of the nervous system. (2) Or we may take each sensori-motor reflex system as the unit and trace its phylogeny through the series of types. This second method has the obvious advantage that one can start with the system in question in some type where it attains maximum development and, having arrived at a thorough knowledge of its anatomy and physiology here, it will be easier to read this schema backwards to the more primitive animals, as well as forwards in its further evolutionary modifications. It is hardly necessary to call attention to the fact that the human nervous system is the least favorable starting point for this sort of a research except for the neo-pallium and its appendages. Each method has its advantages. The monographic treatment of type brains is really far more difficult, even in the lowest vertebrates, because of the difficulty in interpreting such simple undifferentiated pictures and analyzing a complex where there are few salient features. But nature has effected the analysis for us in some of the more specialized types by the hypertrophy of isolated systems; and if, as sometimes happens, the other functional systems are in a primitive or reduced condition, we have a favorable point of approach for a monographic study of the exaggerated functional system (cf. JUDSON HERRICK, '03). The purpose of this study is to make such a detailed analy |