346 K. A. KOCHEll 



])arablo ])laiie. Colls were first drawn using a low power for 

 orientation, each cell numbered on the paper, then the one-sixth 

 objective or the one-twelfth objective was used to project the 

 cell, care being taken to draw always at the same distance from 

 the microscope. The area of the cells was then computed with 

 the use of the polar planimeter. The data are tabulated in 

 table 2, and will be referred to later in connection with the indi- 

 vidual experiments. 



Normal Activity 



Experiment I. Dogs. The animals which served for this experiment 

 were two fox tei-rier puppies from the same litter, three months old. 

 A female was used for activity while the male served for the control. 

 The latter remained quiet in a cage, where he had been kept for several 

 weeks previously. The activity animal was led by a chain on a fast 

 walk into the country; the distance covered was fifteen miles in three 

 and a half hours. This was a considerable feat for a puppy of this 

 size, as the pace meant running all the way for her. At the end of 

 three and a half hours, she was so fatigued that she refused to go any 

 further, and had to be carried home. She was then killed less than 

 one hour after exercise had ceased, the brain and cord at once removed, 

 and sections taken from the lumbar and cervical enlargements, from 

 the cerebellum, and from the cruciate gyrus, and the sections placed 

 in 10 per cent formalin and in Held's fluid. The control dog was killed 

 at the same time, in the same way, and corresponding sections taken 

 from the brain and cord, and placed in the same fixing fluid with those 

 from the 'fatigue' animal. 



MICROSCOPIC STUDY OF THE NERVE CELLS 

 Cervical eyilargement of the cord 



The cells are uniformly stained, the Nissl bodies standing out 

 clear and distinct. In both control and fatigue specimens, there 

 is an occasional cell showing sHghtly clear areas about the nucleus, 

 but this is no more marked in either section, and these cells are 

 as numerous in the control as in the other. Drawings were made 

 with the Leitz camera lucida, using the one-twelfth objective 

 and no. 2 ocular. The camera lucida outlines of the cells and 

 nuclei were traced with a planimeter with the following result : 



Control cells, 43 measured, average area 0.44r square inches. 



