814 



In all these groups small and large representants were compared 

 — except that there is no small proboscidean to be compared with 

 the elephant ^). I have however taken into consideration also the 

 latter because it shows so well the general law in the relation 

 between white and grej matter as will be seen in my table (fig. 1). 



The following method was used : 



The sections coloured after Weigert^Pal were drawn in a pro- 

 jection-apparatus, in about the same size. Since it is only a question 

 of relation the magnification is not of importance, and can only in 

 so far act a part as a stronger magnification enables us to greater 

 exactness in drawing the details of the circumferences. 



These drawings were made on waxplates of .constant thickness"), 

 and the circumference of the grey and white matter cut out. 



The ouicuts were weighed and their relation expressed in percents. 

 They are represented in the table of figure 1. In each column the 

 grey matter is represented by the black colour, the white substance 

 by the white colour; the number under each column indicates the 

 percentage of grey matter. 



In those columns where a large and a small representant of the same 

 order are compared, we constantly see that in the larger representant 

 the relation is very much in favour of the white matter. Equally 

 in the elephant the enormous prevalence of white substance is striking. 



In two animals — Hexanchus and Scylliam — the grey substance is not very 

 compact but sbows a rather reticular arrangement, the openings of the reticulum 

 being filled up with white substance. This made it very difficult to make trust- 

 worthy outcuts, for which reason I have omitted to reproduce the results — 

 which however was not in contrast to the general rule. 



Since the four ptatyrrhine apes did not all differ considerably in size, I have 

 only represented the relation in the smallest and largest monkey. 



The general rule expressed by my table for small and large adult 

 material seems to be equally striking in the development of the 

 centi'al nervous system as appears from the interesting researches of 

 R. Stern ^), who has pointed out that during the development of 

 the spinal cord from infant to adult the white substance increases 



1) The tapir might be used for comparison being nearest akin. This animal 

 however has not been stained. It is fairly large moreover. 



2) As used for waxreconstructions after Born and Peters' method. 



^) R. Stern. Beitrag zur Keuntnisz der Form und Grösze des Rückenmarks 

 querschnittes. Arbelten aus dem Neurologischen Institute der Universitat Wien 

 1908, p. 367. 



