784 THE MOTOR CORTICAL CENTERS OF THE CEREBRUM. 



the motor cortical points by means of a horizontal incision during an attack 

 causes cessation of the attack. If an epileptic attack is of short duration, it is 

 not rarely possible, by extirpation of the cortical center for one extremity, to 

 exclude this alone, while the remainder of the body continues to be agitated by 

 the convulsions. 



Long-continued administration of potassium bromid prevents the possibility 

 of causing epilepsy by irritation of the cortex. 



Chemical irritation is further of particular interest. When in 1887 

 Landois applied to the motor regions a number of substances that occur 

 in urine, for example kreatin, kreatinin, acid potassium phosphate, 

 uratic sediment from human urine, and others, he observed the occur- 

 rence of marked eclamptic (clonic-tonic) convulsions, which were re- 

 peated spontaneously for a considerable time and were followed by pro- 

 found coma (in the dog). Landois does not insist that the uremic con- 

 vulsions in human beings, as well as epileptic convulsions induced 

 through autointoxication, are to be compared with the phenomena 

 observed in his experiments. The sensorial centers are also affected in 

 the same way, the sense of vision suffering especially. 



Certain poisons are capable of exciting convulsions by irritation of the cor- 

 tical centers. Among these are santonin, physostigmin, carbolic acid, acetone 

 (in cases of diabetes), also tannic acid on direct application. Under such cir- 

 cumstances convulsions upon both sides of the body may be excited by irritation 

 of one hemisphere. The convulsions no longer occurred after the cortical centers 

 were removed on both sides. Birds and lower vertebrates exhibit no convul- 

 sions. 



Extirpation of the motor centers gives rise to characteristic derangement 

 of movement in the affected contralateral muscles. Landois, together 

 with other investigators, observed in the dog after destruction of the 

 motor points for the extremities feeble and awkward movements of the 

 latter, such as improper placing of the foot, slipping, yielding, dragging. 

 While some investigators consider these phenomena as transitory only, 

 Landois was able to observe them for months. In dogs, particularly 

 the paws remain paralyzed with respect to all of those movements in 

 which the paws are employed to a certain degree as hands, and which 

 thus are acquired through education. In the course of time the 

 pyramidal tracts degenerate downward and the related muscles undergo 

 atrophy. 



The higher the development of the intelligence in the animals and the more 

 they are required to learn their movements and gradually to subordinate them 

 to the control of the will, the more profound and persistent are the disturbances 

 of movement after destruction of the cortical psychomotor centers. While, in 

 the lower vertebrates, including birds, extirpation of the entire hemispheres does 

 not appreciably affect the movements, the coordinated reflexes sufficing com- 

 pletely for the latter, in the dog extirpation of individual motor centers is attended 

 at times with appreciable permanent derangement of motility, which in apes and 

 human beings becomes intense and long continued. 



Hitzig attributes the disturbances of movement following removal of the motor 

 centers to the loss of muscular consciousness. According to Schiff , tactile sensa- 

 tion alone is lost in consequence of destruction of the motor cortical centers, 

 and it never returns. 



In a dog in which the motor centers for the extremities were destroyed 

 on both sides Landois, in 1876, observed derangement of voluntary movement, 

 which he was first to designate cerebral ataxia; that is the animal was unable to 

 execute coordinated movements for the purpose of walking, standing, etc. He 

 therefore believed, even at that time, that the cortical centers are the direct 

 motor points for the operation of the will and also that conscious sensation of 

 muscular contractions is localized in them. 



