6 A Reconstruction of the Nuclear Masses in 



Throughout this paper, the terms "nuclear material " and " gray matter" 

 have been used almost synonymously. Neither of the terms is satisfactorily 

 descriptive, but by them are meant the collections of nerve-cells with attending 

 neuroglia-elements, which go to make up the easily recognizable nuclei, the 

 various substantias, and the formatio reticularis. Considered narrowly, these 

 masses are merely those in which the cellular elements i)redominatc in amount 

 over the fiber strands. Of the other terms used in this paper, little need be 

 said. "Cephalic," "superior, "and less frequently "upper" are the adjectives 

 applied in the sense of "toward the cerebrum," while "caudal," "inferior," 

 and "lower" are used to designate the direction of "away from the cerel^rum" 

 or "tow^ard the tail." 



METHOD OF RECONSTRUCTION. 



To secure the third dimension in this morphological study, the method 

 of Born was adojjted reconstruction by means of wax plates of uniform 

 thickness. By a projection apparatus, drawings of uniform enlargement 

 were made from a series of sections of the human adult brain-stem. This 

 series of over two thousand serial sections comprises one of the "loan collec- 

 tions" in the neurological series of the Anatomical Department of the Johns 

 Hopkins Medical School. (Brain-Stem No. 2627). The brain-stem was 

 fi.xed in formalin, embedded in celloidin, and cut transversely, the sections 

 being 40 microns in thickness. The staining was done ]iy the Weigert-Pal 

 method, with counterstaining by carmine. In this present work every fifth 

 section was projected with a constant magnification of 15 diameters; the draw- 

 ings were made and then corrected by examination of the slide under low 

 magnification; the corrected drawings were transferred to wax plates and 

 the plates were cut by means of a knife. The magnification of 15 diameters 

 was selected because it secured a i)late of convenient thickness (3 millimeters) 

 and also because it practically coincided with the enlargement used by Miss 

 Sabin in her reconstruction of the brain-stem in the new-born babe (14.5 

 diameters). 



The sections in this series are well stained and no difficulty was experi- 

 enced in differentiating between nuclear material and the fiber bundles. The 

 masses of gray matter were outlined with consideration chiefly for the general 

 appearance of the nuclear mass and with much less regard for the individual 

 cells comprising the mass. This differentiation on this grosser outline leads, 

 it is believed, to a better and truer conception of the mori^hology of the 

 masses. In cases where doubt existed, and in the determination of the final 

 limits of the gray matter under consideration, the identification and location 

 of the characteristic cells of the nucleus were regarded as necessary for the 

 correct establishment of the limits of the nuclear material. Comparison of 

 the results given by l)oth of these methods the first with moderate magnifi- 

 cation, and the second with magnification high enough to i)erniit identifica- 

 tion of characteristic cells showed that in no cas(> would the limits, as 



