488 THE BRAIN. 



rhage, yield results which are sufficiently uniform to show that they 

 depend upon important physiological conditions. In those performed 

 by the committee of the New York Society of Neurology and Electro- 

 logy, the animals were etherized and kept more or less completely under 

 the influence of the anaesthetic during the whole course of the experi- 

 ments. The stimulus employed was a galvanic current from a battery 

 of from 8 to 16 cells, of an intensity just sufficient to be distinctly per- 

 ceptible, but not painful, when applied to the surface of the tongue. 

 The electrodes were rounded platinum points, fixed at a distance of one 

 millimetre apart. They were applied to the surface of the cerebrum in 

 such a manner as not to wound but only to touch it, and were held in 

 contact with the brain for about one second only at each application. 

 The applications were repeated at short intervals at the same spot for 

 from ten to forty times in succession, in order to make sure that the 

 reactions obtained were not accidental. The results show plainly that 

 there are certain limited spots, on the surface of the cerebral convolu- 

 tions, at which the application of a faint galvanic current will cause dis- 

 tinct momentary contraction of separate muscles, or groups of muscles, 

 on the opposite side of the body. These spots correspond in all essential 

 particulars with those discovered by Hitzig, and are near!}', though not 

 quite, uniform in location on the two opposite sides, and in different 

 animals. 



All the centres of motion for the anterior and posterior limbs are 

 situated, in the dog, in the convolution immediately surrounding the 

 frontal fissure (Figs. 161, 162, F), a nearly transverse furrow running 

 outward and forward from the median line, which may be considered 

 as corresponding to the fissure of Rolando in the human brain, but 

 placed farther forward in the dog, owing to the inferior development of 

 the frontal lobe. In a majority of cases, the motor centres for the 

 anterior limbs (3, 4) are situated more in front, near the outer extremity 

 of this fissure ; those for the posterior limbs (5, 6) farther backward and 

 inward. At certain points, movements of flexion are produced, at 

 others, movements of extension ; sometimes flexion of a single paw alone 

 takes place, sometimes flexion or extension, more or less complete, of a 

 whole limb ; and sometimes, at certain spots, there is flexion or extension 

 of the fore and hind limbs together, or partial flexion of one, accompanied 

 by extension of the other. But in the majority of cases, the movements 

 produced are isolated movements of flexion or extension of a single limb. 



The centre for flexion of the head on the neck in the median line (1) 

 is in the lateral and anterior part of the convolution situated in advance 

 of the frontal fissure, where this convolution bends downward and out- 

 ward ; tha.t for flexion of the head on the neck, with rotation toward the 

 side of the stimulus, is in a part of the same convolution (2), situated 

 still farther forward and downward, so as to be invisible in a view of 

 the brain taken from above. 



The centre of motion for the orbicularis oculi, and, according to 

 Hitzig, for the facial muscles generally, is in a region situated upon the 



