This paper presents the physiological and anatomical observations on the effect of cerebral hemispherectomy in four dogs. Two hemis pherectomies were on the right side and two on the left. These animals were sacrificed on the 21st postoperative day, except for one, which was sacrificed on the 14th postoperative day.
In this study one cerebral hemisphere was removed but care was taken to preserve the thalamus and caudate nucleus. However, autopsy showed some damage or necrosis of the basal ganglia in two of the four dogs. In two of the four dogs an infection developed in the operated site but there was no evidence of spread of this infection to the contralateral side.
The postoperative physiological findings were as follows: All experimental dogs showed-heiniparesis on the contralateral side but they could get up and walk within a week after operation and this hemiparesis gradually improved so that two or three weeks after operation they showed almost equal or only slightly decreased motor function in the contralateral extremities. Usually the hindlimb was - more severely affected than the forelimb.
The pensistent neurological findings were a contralateral homonymous hemianopsia and slightly, decreased sensation on the contralateral side. When they walked, they turned to the ipsilateral side. - This was considered due to the contralateral homonymous hemianopsia.
The anatomical findings were as follows: In order to minimize postomortem artifacts the brain stem and spinal cord of all experimental animals were removed under deep,.l nembutal anesthesia. The brain stem and spinal cord were stained with the Swank-Davenport staining method.
All experimental animals showed almost complete degeneration in the ipsilateral crus, pyramidal bundles, pyramid, decussating fibers and in the contralateral lateral pyramidal tract but no evidence of degeneration was observed in the contralateral crus, pyramidal bundles, pyramid, or the decussating fibers.
Degenerated fibers in the contralateral lateral pyramidal tract were traced down to the lower thoracic or lumbar level. But there was no evidence of degeneration in the ipsilateral lateral pyramidal tract in all dogs nor in the ipsilateral anterior pyramindal tract in three of the four dogs. In one dog there were a few degenerated fibers in the ipsilateral anterior pyramidal tract. These were traced down to the T 10 level.
In the midbrain sections there were a few scattered degenerated fibers in the ipsilateral anterolateral margin of the central gray matter (antero-lateral columnar fibers of Boyce, 1895) and in the anterior decussating fibers which run to the inner border of the contralateral crus (lateral columner fibers of Boyce, 1895). These degenerated fibers were seen only in two of the four dogs.
At the anterior border of the dorsal spinocerebellar tract where the accessory pyramidal bundle of Probst (1899) is located, there were a few degenerated fibers on the ipsilateral side in one of the four dogs. These fibers were found from the section at the level of. pyramidal decussation to the. C
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