A RECONSTRUCTIO-N OF THE NUCLEAR MASSES L\ THE LOWEl 

 PORTION OF THE HUMAN BRAIX-STEM. 



INTRODUCTORY. 



CHARACTER OF WORK UNDERTAKEN. 



For the purj^ose of securing more accurate knowledge of the masses of 

 gray matter in the rhomhencejihalon, this work was undertaken, with the 

 idea that l^y a careful wax-plate reconstruction of the nuclear material in one 

 brain-stem the i)resent conception of their morphology might be advanced. 

 The study has been i)urely morphological, with no attempt to introduce other 

 elements. With the realization that considerable indi^idual Aariation exists, 

 even on macroscopic examination in the surface anatomy of the medulla and 

 pons, the conclusion becomes obvious that the mor])hological studies here 

 presented deal with only one brain-stem and in the finer details the findings 

 will not endure for all types. However, it is believed that such a study of 

 the form of the different gray masses in the caudal portion of the brain-stem 

 may prove advantageous in the ultimate establishment of the finer anatomy 

 and may perhaps serve as a basis for somewhat more extensive studies. 



In order that the model might exhibit as many of the characteristics of 

 the morphology of the medulla and pons as possible, different masses were 

 retained in i)art on the two sides of the median raphe. In the most caudal 

 portions, the masses modeled are identical, but at the decussatio pyramidum 

 the outer limits of the formatio reticularis are modeled on the one side, while 

 on the other the anterior column is sharply cut off from the central gray 

 matter. In this way the scattered masses of the formatio are brought out, 

 as well as the corresjjonding separation of the anterior column from the 

 nuclear material about the central canal. This modeling of the formatio 

 reticularis is continued cephalad, so that the one side of the reconstruction 

 exhibits the mor]ihology of the formatio reticularis and the markings of the 

 floor of the fourth ventricle, while the opposite half shows the isolated nuclear 

 masses segregated from each other. These differences in the two halves of 

 the reconstruction are explained in more detail in tlie \arious descriptions 

 com])rising this paper. 



The literature on the morphology of these nuclear structures in the human 

 brain-stem is wofully scant. The most important studies are those made by 

 Dr. Florence t^abin, of the reconstruction of the nuclear masses and fiber paths 

 of the brain-stem of a new-born babe. Most of the other i-eferences to the 

 literature deal not with actual morphology, but with i)lotted limits, and it is 

 to avoid such diagi'ammatic representations that this study is i)r(s(>nt('d. 



