EXPERIMENTS. 183 



Experiment VI A. 



August n, ii A. M. Exposed the spinal cord, and made a longitudinal median section 

 through the first abdominal ganglion. F.I. Rhythmical contractions of the gills followed, lasting 

 a short time. 



Experiment VI B. 



The right cord was then cut across about midway between the brain and the first abdominal 

 ganglion. F.I I. 



I. Respiratory Reflexes. a. At first no reflexes followed the section, but after one or 

 two minutes respiratory movements began. The left gills were raised much higher than the 

 right, the latter being apparently dragged up by the left gills, rather than by their own action. 

 When respiratory movements ceased, the left gills remained in a higher position than the right. 



b. When placed in the water, the respiration was at first about normal, but in a few min- 

 utes it almost ceased, leaving the left gills moving slowly, the right motionless. After about an 

 hour, respiration ceased, leaving the left gills raised, and the right closely pressed against the 

 abdomen. 



II. Abdomino-thoracic Reflexes. a. On placing the hand on the right margin of the 

 abdomen, all the left legs are promptly raised, remaining in that position till the hand is removed, 

 when they again fall back slowly into the thorax. The right legs are also raised, but after the 

 left. 



b. Hand placed on the left margin of the abdomen causes raising of the right legs (but the 

 response is not as prompt and vigorous as that of the left legs in the previous experiment). The 

 left legs are not raised, but their chelae stir uneasily. 



c. Repeated a and b two hours later with the same results. 



d. Stimulating with a weak electric current at b, causes contractions of the right gills, also 

 slight movements of the left gills (see below); at c, causes contractions of the left legs and the 

 gills on both sides; at a, causes contractions of the right legs. 



e. 2.30 P. M. Applying electrodes at a, the right gills are slightly raised, and then moved 

 back and forth faintly as in respiration. Left gills move much less than right. 



/. Stimulating at f, obtain movements of left gills and partial ones of the right, and with 

 vigorous and immediate movements of the left legs. 



g. Stimulation at a, causes immediate movements of the right legs only. 



We thus see that stimuli applied directly to the spinal cord produce uncrossed reflexes of 

 the appendages anterior to the cut, and both crossed and uncrossed below the cut. 



But temperature impulses, starting on the sides of the abdomen and traveling centripetally, 

 produce both crossed and uncrossed reflexes in the thorax. It is not clear why direct stimulation 

 of the spinal cord should produce only uncrossed impulses above the point of stimulation. 



Experiment VI C. 



3.30 P. M. Made an accurate sagittal cut through the vagus neuromeres, care being taken 

 not to cut the first three or four post-oral commissures. F.I 1 1 



a. Stimulating at a or c, produced leg movements of the corresponding side, as before. 



b. But stimulation of the margin of the abdomen and gills, with the hand, produced no 

 leg reflexes, although breathing on the legs, or dropping tepid water on them, produced prompt 

 movements of the same. 



It would thus appear that all the uncrossed temperature impulses started in the abdomen 

 cross in the vagus neuromeres. 



