A CASE OF CYCLOPIA 215 



TECHNIQUE 



Without further examination, the brain stem and thalamic mass 

 were imbedded in celloidin. When this had been hardened suffi- 

 ciently it was subdivided into blocks of convenient size and serial 

 sections made 45 microns in thickness. Sections were selected 

 at suitable intervals (about every tenth, but in places every 

 fifth section) and stained by a modified Weigert method and 

 counterstained with Upson's carmine. For comparison, a sim- 

 ilar series was prepared from the brain stem and left cerebral 

 hemisphere of a normal full term foetus. 



Blocks also were cut from selected areas of the cortex of the 

 cerebral vesicle and sections of various thicknesses were exam- 

 ined. For comparison, sections were studied from the cortex 

 of the right cerebral hemisphere of the normal foetus mentioned 

 above. In each case the following stains were used: modified 

 Weigert, modified Nissl, and a simple hematoxylin-eosin stain. 



The drawings of the microscopic preparations from the brain 

 stem and cerebral cortex have been made with the aid of a Leitz 

 projectoscope. 



MICROSCOPIC DESCRIPTION OF THE BRAIN 



Brain stem and cerebellum (figs. 24 to 47) 



On comparison with sections taken from the normal brain 

 stem at birth, this series shows several outstanding points of 

 difference. There is a complete absence of the crura cerebri in 

 the midbrain, the fasciculi longitudinales pyramidales in the 

 pons and the pyramids in the medulla. The marked S-shaped 

 flexure of the brain stem causes sections, which are transverse 

 to the long axes of the medulla and midbrain, to be oblique and 

 horizontal in the intervening regions. There is also a marked 

 deficiency in the number of well meduUated fibers present 

 throughout. The development of the myelin sheaths has evi- 

 dently been retarded. In the region of the midbrain the pia 

 has been greatly thickened and forms a thick capsule which 

 entirely masked the surface markings over this area in the recent 

 state. 



