462 



W. M. SMALLWOOD. 



this continued respiratory activity in the gill region but the results 

 were not satisfactory. 



The tank in which these fish were kept was in a shady part of 

 the room and for weeks at a time the fish were not disturbed. 

 It would seem as if the sensory components of these two nerves 

 were as free from stimuli as it is possible to have a living animal 

 in its normal environment. Under such conditions, the cell 



FIG. 4. Microphotograph of nerve colls in tenth ganglion. 



258 X. 



Magnification 



bodies in the tenth ganglion would certainly not be in a state 

 of fatigue. Rather the reverse should be the condition, i. e., 

 a condition of rest. The nerve cells which immediately govern 

 the contraction of the muscles of the gills are located near the 

 floor and at one side of the medulla. In selecting these as the 

 motor nerves of the vagus for the gills, I am accepting Herrick's 

 conclusions as already cited. If these are the correct cells to 

 select for this study, then we should expect them to be in just 

 the opposite condition to the sensory cells in the vagus ganglion 

 because they have been continuously transmitting motor stimuli. 

 The microphotographs, Figs. 4 and 5, clearly indicate that the 



