(4) Spine was bent in the thoracic region concave to the homonymous

side.

(b) From second week to two and a half months,

(1) Locomotion improved very little.

(2) All the other symptoms had considerably improved in one week; but were far from normal, and were characteristically present after stimulation two and a half months afterward.

XV. Bilateral excision of everything anterior to the medulla.

(a) From a half hour to three days,

(1) Croak reflex is difficult to elicit.

(2) Turning over reflex is inhibited.

(3) In addition, all symptoms as after operation VI and XIII.

(b) Four days to one month after operation,

(1) Collective symptoms of operation VI and XIII.

(2) Croak and turn-over reflex are normal.

(3) Swallowing, heart action and respiratory reflexes, and sense of equilibrium are intact.

XVI. Unilateral Excision of the right side of the medulla anterior to the calamus scriptorius.

The observations pertaining to this operation necessitate recording at shorter intervals. I shall use the same number for an observation throughout, and after noting a phenomenon once, shall not mention it again until at the end, unless it changes.

(1) No reaction with head or body movements on rotating table.
(2) Body, especially anterior portion and head, are lower on homony-
mous side than on crossed side.

(3) Legs on crossed side, especially the posterior one, are far extended
and abducted.

(4) Legs on homonymous side, especially anterior, are superflexed and adducted.

(5) Forced rotatory movements around the sagittal axis of body toward
the homonymous side are the sole movements.

(6) Abdominal respiration on the homonymous side is stopped.
(7) Narial and oral respiratory movements are bilaterally normal.

B. One half to five hours after operating.

(8) Eye reflex to pressure on the homonymous side is gone but is

normal on the crossed side.

(9) Crossed eye is turned upward and outward.

(10) Homonymous eye is turned downward and inward.

(11) Homonymous eye is turned upward synchronously with inspiration; and downward with expiration.

(12) Nictitating membrane of homonymous eye is evidently beyond the animal's control; it covers the eye, especially when this moves

downward.

(13) Croak reflex elicited only in a depressed degree.

(14) Swallowing reflex is normal.

(15) Spine and neck curved as after operation XIV.

(16) Tremor on both sides; but strongest on the homonymous side.
(17) Weakness of muscles in proportion to tremor.

(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.

(b) 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,

(1a) Same as after one day but in addition, sometimes a circular movement of the body in clockwise direction after rotating the table.

(1b) 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.

XX.

XXI.

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.

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.

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. XVIII1.

SECTION II. THE PERIPHERAL GUSTATORY SYSTEM IN FISHES.

SECTION III. THE CENTRAL GUSTATORY SYSTEM OF CYPRINOID FISHES.

I.

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.
General Morphology of the Gustatory System.

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.