1 82 FUNCTIONS OF THE BRAIN. 



the electrodes, peculiar rhythmical contractions followed. The movements stopped in a few 

 moments. 



b. On rubbing very gently a small piece of clam on the gills, the movements began again, 

 but more vigorous than before. On returning the crab to the water, the movements, which 

 had meantime ceased, began again and continued with some interruption, for purposes of 

 experimentation, for several hours. These movements were as follows: i. The abdominal 

 appendages remained well elevated, pulsating in short strokes, once about every one and one- 

 half second, for twenty-five seconds. 2. Two full vertical pulsations then follow, each one being 

 a vigorous flattening of the appendages against the abdomen, followed by an elevation of the 

 same to their full height. 3. They move repeatedly back and forth across the median line, 

 rubbing the posterior surface of one appendage over the anterior surface of its mate, as though 

 rubbing or washing the gills. They may remain crossed and motionless for several seconds, 

 but finally return to their first position. 4. One full pulsation followed by 5. a long pause of 

 twenty-five seconds, and then the whole begins again. One whole series of movements takes 

 place in about seventy seconds, but this period may be gradually prolonged till all the move- 

 ments cease. 



c. When the crab was taken from the water and placed on its back, the movements grad- 

 ually ceased. 



d. Breathing on the gills produced only a slight contraction of the same. A drop of water 

 produced two or three faint pulsations. Scratching the abdominal appendages with the fingers, 

 or with a stick produced no result, but on rubbing them with a small bit of clam, the compli- 

 cated series of rhythmical movements described in b began at once. 



Experiment V A. 



10.30 A. M. Large female. Sectioned both crura back of chelicerai. All spontaneous 

 movements cease. (Fig. 113, E.I.} 



I. Thoracic Reflexes. a. Hand placed on either margin of the thorax causes contraction 

 of the gills of the same side, and later the raising of the legs of the opposite side. In both cases, 

 the legs on the side stimulated start slightly, but are not raised. No purposeful movements of 

 the legs are made to remove the irritation. 



II. Gustatory Reflexes. Three hours after the operation no chewing movements could 

 be produced by stimulating the jaws. 



Experiment V B. 



3 P. M. Sectioned the right half of the ventral cord, in front of the first abdominal ganglion, 

 .77. 



I. Abdominal-thoracic Reflexes. a. Hand placed on the left margin of the abdomen 

 caused raising of the right legs, first to sixth. Hand placed on the right margin, caused move- 

 ment of the fifth and sixth legs on the opposite side. 



These two experiments show that impulses cross both above, and below, the cut, 77. 



Experiment V C. 



3.30 P. M. Made a sagittal cut through the vagus neuromeres, but without cutting the 

 free, thoracic cross commissures, .777. 



I. Abdomino-thoracic Reflexes. At first all crossed abdomino-thoracic reflexes ceased. 



a. A few minutes later, placing hand on right margin of abdomen causes the fourth, fifth, 

 and sixth legs of left side to be raised. 



b. Hand placed on left side of abdomen causes fifth and sixth legs of same side to be raised, 

 but these movements are not so strong as when the right side of the abdomen is stimulated. 



Crab died after about twenty-four hours. 



