THE CEREBRUM, AND ITS FUNCTIONS. 701 



nagcl from the results of his experiments in the injection of chromic acid 

 into the brain cortex. 1 Schiff 2 regards the movements resulting from stimu- 

 lation of the hemispheres as of a reflex nature, but denies the existence of 

 centres which exert any direct influence on the muscles of animal life. He 

 docribes the results of ablation of these centres as due to the loss of muscu- 

 lar sense in the parts. Hermann, 3 though admitting the fact of definite 

 movements being excited by localized stimulation of certain cortical regions, 

 denies that this proves the existence of motor centres in the hemispheres, 

 and grounds his opinion on the fact that dogs recover perfectly from the 

 effects of destruction of the so-called motor centres of the limbs, and regain 

 complete control of their movements. The interpretation which Ferrier 

 puts upon his experiments differs essentially from any of the foregoing. He 

 regards the movements which result from stimulation as indications of exci- 

 tation of centres concerned in voluntary or purposive action, or of centres 

 of expression and sensation. The motor portion of the brain is situated 

 anteriorly and corresponds with the medullary expansion of the fibres from 

 the corpus striatum, while the sensory portion corresponds with the medul- 

 lary expansion from the optic thalamus. The destruction of a motor centre 

 causes paralysis of voluntary motion in respect to the actions which are ex- 

 cited by stimulation of the same centre. This paralysis, however, is only 

 complete in cases of movements which are quite independent of each other. 

 It is seen more especially in the case of the monkey, which, like man, is 

 capable of highly complex and independent movements. In dogs and quad- 

 rupeds generally, owing to the fact of the movements being usually associated 

 on both sides, the destruction of a motor centre in one hemisphere does not 

 cause complete voluntary paralysis. Under the influence of the other hemi- 

 sphere action of both sides may be caused by the agency of the lower gan- 

 glia. Hence a dog may rapidly recover from the paralysis of voluntary 

 motion, which manifests itself immediately after the destruction of the motor 

 centres in the opposite hemisphere. This explanation is in accordance with 

 the theory of Dr. Broad bent, who accounts for the fact that paralysis from 

 brain disease affects the arm more than the leg, owing to the bilateral co- 

 ordination in each hemisphere of movements usually associated together. 

 Hence the motor centres in the brain are regarded by Ferrier as the differ- 

 entiated apparatus of voluntary muscular action. At the same time they 

 form what he terms the motor substrata of intellect, by being the centres of 

 memory of muscular actions. Hence he explains how the loss of speech is 



1 Nothnagel ( Virchow's Archiv, Bd Ivii, p. 184, and Iviii, p. 420) found on inject 

 ing a solution of chromic acid into a point about 14 mm. (half an inch) from the 

 anterior extremity of the cerebral hemisphere in rabbits, and about T a jth of an inch 

 from the median fissure, that the opposite Ibrepaw dragged in walking, and could be 

 placed in the mo.-t awkward positions without thn animal resenting it, or attempting 

 to withdraw it. It was, however, neither insensible nor paralyzed, it only appeared 

 to have lost its muscular sense. A similar spot influencing both the fore and hind 

 legs exists at the outer extremity of the gyrus post-frontalis. The affection is tran- 

 sitory and disappears in a few weeks Other motor paralyses were observed with in- 

 jections made into various parts of the white substance. He finds a spot near the 

 middle and inner part of the corpus striatum, which when injured leads in the course 

 of a few minutes to violent leaping and springing forward movements, which con- 

 tinue for a quarter or half an hour till the animal drops exhausted ; he terms this 

 spot the nodus ruf'sorins. Injury to a spot situated at the posterior extremity of the 

 single sulciis of the brain of the rabbit, is followed by similar springing movements, 

 which after a few minutes cease entirely. Nothnagel found that ablation or destruc- 

 tion of the lenticular nucleus was followed by the same effects as removal of the 

 cerebral hemisphere of the same side. See also Fournie, Comptes Rend., t. Ixxvii, 

 No. 5. 



2 Archiv f. Experiment. Pathol. und Pharmakologie, 1874, Bd. iii. 



3 Archiv f. Physiologic, Bd. x, 1875. 



