Method XX 1 1 5 



anteriores form two slender crescents united across the mid- 

 line by a narrow commissura grisea which occurs relatively 

 nearer to the. ventral side of the medulla spinalis. In this 

 region the substantia alba is both relatively and absolutely 

 greater in amount than in the regions below it. Especially note 

 the increase in the funiculi posteriores. Can the funiculus 

 gracilis be distinguished from the funiculus cuneatus ? How 

 does the nucleus dorsalis modify the shape of the columna pos- 

 terior ? Is there a columna lateralis ? Formatio reticularis ? 



4. In the pars cervicalis there is a decided increase in the 

 absolute amount of substantia alba. The columnae anteriores 

 are much thicker than the columnae posteriores, and there is a 

 well-marked columna lateralis and formatio reticularis. In the 

 funiculi posteriores, the funiculus gracilis is now more easily 

 distinguished from the funiculus cuneatus. The funiculi late- 

 rales have so increased as to give the section an oval shape. 

 What is the relative size of the funiculi anteriores ? 



5. A section taken at about the level of the second N. 

 cervicalis will show that the substantia grisea has assumed a 

 shape and thickness similar to that in the pars thoracalis, while 

 the substantia alba has decreased but little. Why should it 

 decrease at all ? What are the funiculi proprii (ground 

 bundles) ? To what causes are the intumescentiae due ? 

 Explain the fact that both the ascending and the descending 

 funiculi increase in amount as we pass from the conus medul- 

 laris toward the encephalon (brain). 



B. ENCEPHALON (THE BRAES).' 

 I. EXTERNAL FEATURES. 



(fl') Meninges : — Lay the encephalon dorsal surface upward. 

 From one side gently lift the cap of dura mater encephali left 

 on. in the removal of the specimen, and identify the arachnoidea 

 encephali, the cavum subdurale, the cavum subrachnoidale, the 

 pia mater encephali, and the subarachnoid trabeculae connecting 



■ It is assumed that the specimen has been removed and preserved for dissection 

 as directed in Method XIX. 



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