184 FUNCTIONS OF THE BRAIN. 



Experiment VII — A. 



Adult male. Sectioned right cord (Fig. 113, G.I). Twitching of the right operculum and; 

 first right gill followed the operation. 



Experiment VII — B. 



Cut the whole ventral cord in halves, lengthwise, G.I I. 



a. The caudal spine is thrown toward the left and remains so permanently. 



b. On breathing on the abdomen and gills, the gills are retracted and the right legs alone 

 are raised. 



c. Placing the fingers- on the left margin of the abdomen causes the raising of all the right 

 legs; the legs are strongly flexed and the points thrown medianly and backward. ■ 



d. Hand on the right side produces no results, except that in some cases there is a slight 

 start of the left legs and a faint gaping of the chelae, but no movement at all resembling those seen 

 on the opposite side of the body. This impulse probably reaches the forebrain through the 

 longitudinal integumentary nerve. (Fig. 70.) 



c One hour later. Repeated several times d, h, and c, with same results. 



Experiment VIII. 



July 29. Male. The right and left halves of the cord were separated behind the opercular 

 neuromere, by a median, longitudinal cut extending through all the abdominal neuromeres. 

 All the free, post-oral commissures of the brain were also cut, leaving the vagus commissures 

 intact. 



I. Abdominal and Abdomino-thoracic Reflexes. — July 30. Stimulation of the left 

 side of the abdomen caused a drawing down of the left gills and an immediate and strong upward 

 movement of the right legs, followed by a slight raising of the legs on the left side. Stimulation 

 of the right side of the abdomen in the same way, produced the same result, and vice versa. 

 In both cases there was a movement of the tail toward the stimulated side. 



The experiment shows unimpaired crossing of impulses in the vagus neuromeres. 



II. Respiration. — July 29. The right and left halves of the gills were breathing in alter- 

 nation, the gills on the right side being raised while those on the left were depressed. The 

 coordination of the respiratory movements was perfect longitudinally, but the two sides were 

 beating independently. 



Experiment IX. 



I. Purposeful Reflexes of the Sixth Legs. — July 15. Male. Transected the right half 

 of the cord between the first and second gill neuromeres. (Fig. 113, H.g.) 



July 18 and 19. a. Stimulation of the left side of the abdomen. Caused a drawing down 

 of the gills on the same side, together with a spasmodic, upward, non-purposeful movement of 

 the legs on the right side, followed by a purposeful movement of the sixth leg on the left side. 



b. Stimulation of the right side of the abdomen gave same results vice versa, except that 

 in this case the sixth left leg (as before) performed the purposeful movement, the sixth on the 

 right being merely raised. 



Abdominal stimulation produced no purposeful movements of the sixth leg on the cut side. 



II. Yawning. — After the crab had been out of water for about an hour, it would yawn, 

 the operculum and the first gill, both right and left, moving in the usual way, while the gills 

 behind the cut behaved as follows: The left gills were raised in time with the operculum and 

 first gill, although they were not raised as high as in the normal animal. The right gills did not 

 move at all, except as they were slightly dragged upward by the left. 



