421 



Nachdruck verboten. 



Description of a Stage in tlie Deyelopment of the 

 flnman Cerehelium. 



By J. W. Langelaan M. D., Professor in the University of Leyden. 



With 7 Figures. 



The cerebellum is taken from a human embryo with a rump- 

 vertex-length of 55 mm ; the age of the embryo is estimated between 

 the middle and the end of the third month. The embryo was fixed 

 in toto in 10 7o formalin and hardened in alcohol ; the head was cut 

 off along the base of the cranium and imbedded in paraffin. The 

 sections were 10 ft thick and stained with haematoxyline and eosine. 

 The plane of section was fronto-transverse in respect of the fore- 

 brain, and fronto-longitudinal in respect of the hind-brain in consequence 

 of the flexure of the neural tube. 



For the sake of orientation I will designate the direction given 

 by the line of intersection of the median plane and the plane of 

 section as supero-inferior; the direction perpendicular to the plane of 

 section as antero-posterior. Measured along this latter axis, Figure 1 

 shows a section which is at a distance of 0.4 mm from the posterior 

 pole of the cerebellum, in Figure 2 this distance is 1.0 mm, in Figure 3 

 3.3 mm and in Figure 4 it is 4.7 mm. The greatest antero-posterior 

 diameter of the cerebellum amounts to 5.1 mm. 



It ensues from a graphical reconstruction, that the superior sur- 

 face of the cerebellum is narrowest in its middle region and broader 

 in the lateral regions, these latter parts being somewhat inclined towards 

 the mesencephalon. This surface is arched in antero-posterior direction 

 and from mesial to lateral. Laterally where the cerebellum embraces 

 the rhombencephalon, the curvature increases. A deep and large groove, 

 the fossa rhombomesencephalica separates the cerebellum from the mes- 

 encephalon. By this groove the wall of the neural tube is folded in. 

 The infolded part, the plica encephali dorsalis (Fig. 2), forms the 

 isthmus-region of the brain. On its ventricular surface this region 

 shows a transverse shallow groove, which is also described by Kuithan 

 in the sheep. 



