( 386 ) 



Now the signs of y', 6' and &' remain nnelianged for 0<^ ,??<^rt 



3t 



and for a varying' between and — , so that also hero the sign of 



tlie extinction in adjoining globe octants will be alternately positive 

 and negative. The points in wliich eijuivalent isogyres in the systems 

 ^'' and r/)" intersect, indicate tlie places of the i)olës of the sections, 

 in which symmetrical extinction with j-espect to the cleavage planes 

 K (100) and ij (010) visible in the slice is observed. So there 

 ip' + ry = 2//' - (^' + ff') = 0. 

 2//' = <9' + ^" 

 The curve OA = V. If the axis-angle dimhiishes, ^1 gradually 

 approaches 0; the isogyres (p' and cp" approach a symmetrical direction 

 with regard to the axes OP and OQ, so that the curve, connecting 

 their points of intersection, draws nearer and nearei- to the straight 

 line, and at last, when T^ has become =: 0, and .1 coincides with O, 

 passes into the sti-aight line which divides the angle J^OQ into two 

 equal parts. For V=^0 i/' becomes ^0, so: 



<9' + Ö" = 



si?i X tg a — siVj x cot « =: 



ty a = cot a 



so that the geometrical place of the points of intersection of the 

 isogyres (p' and ip", i.e. that of the points of symmetrical extinction, 

 is represented by the line 



a = 45°. 



Anatomy. — "'On asceml'my degeneration after [)art'ial section of 

 the spinal cord." By Dr. S. J. de Lange. (Communicated by 

 Prof. C. Winkler). 



(Communicated in the meeting of Nuvembtr 30, 1907). 



The following researches have been made with the purpose of 

 investigating whether there exist any connections between the spinal 

 cord and the ascending fasciculus longitudinalis dorsalis, a)id on 

 the other hand to ascertain once more the course of the ascending 

 anterolateral fascicle of Gowers and its relation to the dorso-lateral 

 fasciculi of the cerebellum. 



From the extensive literature on this subject 1 will but rarely 

 quote something, whenever the results obtained by others do not 

 accord with my observations. The drawings are taken after four 



