8 A Rcco7}struc(ion nf the Nuclear Mames in 



posterior plane was to be decided. It was tliought that possibly there might 

 be found a constant relationship between some definite point in the teg- 

 mentum and a point in the basilar portion of the brain-stem. Many points 

 in several sectioned brain-stems were tested for this desired constanc.y in 

 relationship, but no two points could be established \\liicli maintained the 

 same relative positions in different brains. For the determination of this 

 antero-posterior jilane, which in sections of the adult lower l^rain-stem is 

 least imjjortant of all, the use of the external form and of the floor of the 

 fourth ventricle was necessary. 



The wax plates were cut out along the lines indicating the external form 

 of the section and were then piled with reference to the three jilanes, the 

 whole giving a very accurate reproduction of the external form of the brain- 

 stem in its lower portion. Definite points were made on successive plates 

 to give the relationship of plate to plate and reconstruction of the nuclear 

 masses was begun. The portions of the plate to be modeled were preserved, 

 together with the ]X)ints to show the relationship to the adjoining plates, and 

 the remainder of the plate was cut away. The relations of the individual 

 nuclear masses to the whole were preser\-ed by means of wax l)ridges left 

 in the original plate, and these bridges were cut away as soon as the nuclear 

 mass was fixed in its position. 



As far as i^ossible, no fusion of wax plates was resorted to until a con- 

 siderable number of plates had been piled together. The object of this pro- 

 cedure was to avoid the introduction of chance variations in the j^lates, as 

 will necessarily occur if the fusion be done as each plate is added. Owing to 

 the com])lexity of the inferior olivary nucleus, such fusion had to lie done as 

 each ])late was added, but it is felt that additional information regarding its 

 complexity is probably add(Ml in this one case. 



The brain-stem from which the sections used in this reconstruction were 

 cut was embedded in celloidin in several individual l)locks. In the ]iortion 

 of the series here involved tlu-ee blocks were concerned and compensation 

 for the tissue lost in the transition from the first to the second and from the 

 second to the third blocks had to be made. The second block was somewhat 

 distorted and to make the plates rei)resenting the second block coincide with 

 those of the first the magnihcation of 15 diameters had to be changed in both 

 antero-jjosterior and lateral dimensions. With this correction applied, the 

 plates of the third block with the uniform enlargements of 15 times Htted 

 exactly the resultant model. The corrections for loss of tissue amounted 

 to 2 plates on one side between sections 345 and 350: in the s(>cond instance 

 to 1| plates l)etween sections 700 and 705. 



In the drawings of the completed reconstruction, the representations 

 have been made from a single viewpoint, in i)ersi)ective, which is taken from 

 the level of section 000. Tliis difference between jierspective and geometric 

 rei)re.sentation results in some foreshortening, which is most marked in the 

 spinal segment of the model. 



