142 Journal of Comparative Neurology. 



probable that dehydration results in dimensions less than the 

 normal and it is therefore more than probable that the dimen- 

 sions of the various parts of the stained sections measured by 

 the author are somewhat less than had the material been sub- 

 jected fresh to the action of Muller's fluid. 



The author chose stained sections in order to get the di- 

 mensions of the various localities more accurately than was 

 possible from the undifferentiated block. Instead of photo- 

 graphs of the sections, the Edinger projection apparatus was 

 used with the aid of transmitted light. With this apparatus the 

 image of the object is thrown horizontally upon the table and 

 directly under the hand of the observer. Distortion is impos- 

 sible. The sharpness of the image is only a matter of focussing 

 and the required enlargement is easily obtained by adjustment 

 of the apparatus and can be accurately determined by measure- 

 ment of the image. The projection was done in a dark room. 

 In order to reduce the error, each section from which the fol- 

 lowing measurements were made, was enlarged exactly ten di- 

 ameters. The image thus enlarged was sharply focussed on 

 white paper pinned to the table. The outlines of the various 

 parts of the section were then carefully traced out with a sharp- 

 pointed pencil. The outline-drawings thus obtained were re- 

 moved and the dimensions of the various localities measured in 

 millimeters according to the scheme shown in text-figure I. 

 These then were reduced to the normal dimensions by divid- 

 ing each result by ten. 



The changes in the form of the gray figure and the rela- 

 tions of substantia grisea to substantia alba can be easily read 

 from Table II. In general, the changes which appear in passing 

 through the cervical into the thoracic segments consist in a uni- 

 form decrease in all the parts. In the mid-thoracic region the 

 gray figure becomes relatively quite small (see Fig. ii, plate 

 XII). Kopsch's table shows that it begins to increase again in 

 thoracic XV. Two series of changes can be read in the parts 

 of the gray figure; viz., changes in size and changes in posi- 

 tion. The latter are indicated in the measurements of the width 

 of the anterior and posterior funiculi (measurements 6, 9 and 



