330 Journal of Comparative Neurology. 



In the enumeration of the fibers contained in the sections, 

 two methods were employed. 



If the section was too large for the whole of it to come 

 easily into the field of the microscope with a combination of 

 lenses giving about 700 diameters and with the camera lucida 

 attached, the photographic method, devised and first employed 

 in this laboratory, was always used. This method of photo- 

 graphing the section and counting the fibers represented in the 

 photograph by means of a counting machine with an automatic 

 register, and at the same time controlling the counting by hav- 

 ing the section itself under the microscope, has been given in 

 full detail in the paper above cited. 



When, however, the section was small enough to be suffi- 

 ciently magnified to separate and distinguish all the smaller 

 fibers and decide cases that would be doubtful under lower 

 powers, and at the same time come well into the field of the 

 microscope, the following modification of the net method was 

 used. 



An ordinary net micrometer was placed in an eye-piece 

 magnifying the squares to the desired size, and the eye-piece 

 so adjusted that the lines of the net appeared sharp and black. 

 Then the camera was adjusted and the images of both the nerve 

 section and the net were thrown on a sheet of unruled white 

 paper placed close to the foot of the microscope. Both the 

 projected outline of the section and that part of the net cover- 

 ing it, were then carefully marked out on the paper. Thus 

 resulted a ring transcribed with a series of uniform squares. 

 The camera was then removed and the counting begun. 



The number of fibers found in each square in the micro- 

 scope was separately recorded in the corresponding square on 

 the paper. In cases in which the cross section of a fiber was 

 cut by a line of the net, one of two signs was used to avoid 

 the fiber being counted twice, or its omission. If it was to be 

 included among the fibers in the square under consideration at 

 the moment, a heavy black dot was made on that part of the 

 line on the paper corresponding to that part of the line in the 

 microscope which cut the fiber. If, rather, the fiber belonged 



