Hardesty, Medulla Spinalis of the Elephant. 151 



would tend to produce a more marked increase in their thickness 

 in passing- cephalad. From what has just been shown, it is hardly 

 probable that the lateral funiculi are largely contributed to by 

 pyramidal axones. In fact, these fasciculi are relatively most 

 bulky at the level of the decussatio pyramidum (Fig. 4) where, 

 if they were increased by the addition of a crossed pyramidal 

 tract, they would only be in the process of receiving this addi- 

 tion and would therefore, instead of being thicker, be less 

 bulky than at the levels immediately Oelow. The width of the 

 funiculi laterales in the section shown in Figure 4 is 10 mm., 

 while at the 1st cervical segment. Table II shows it to be 9/5 

 mm. It will be remembered that a transverse section of the 

 human medulla oblongata is approximately circular at the level 

 of the decussatio pyramidum. The same will be recalled for 

 other specimens in which, at this level, the pyramids, conducive 

 as such to a greater dorso-ventral diameter, are in the process 

 of crossing over to increase the funiculi laterales and the lat- 

 eral diameter of the specimen. 



In passing toward the cervical region, Table II shows that in 

 the more cephalic thoracic segments there is a tendency toward 

 a slight increase in the width of the funiculi laterales. This 

 increase is no doubt due, at least in part, to an increase in the 

 abundance of the fasciculus proprius lateralis (lateral ground 

 bundle) attendant upon the increase in the substantia grisea 

 which begins in these segments. But in addition to this, the 

 peculiar appearance of the nucleus dorsalis (Clarke's column) 

 lends a partial explanation for this increase in the funiculi later- 

 ales in the first thoracic segments. Our present knowledge of 

 this nucleus is to the effect that the neurones whose cell-bodies 

 are situated within it receive their stimuli from afferent axones, 

 and collaterals of such, which enter the medulla spinalis by way 

 of the radix posterior, and that the majority of the neurones 

 of the nucleus send their axones over to the lateral periphery of 

 the same side where they join the ascending fasciculus cerebello- 

 spinalis (direct cerebellar tract). A study of the sections goes 

 to show that in the elephant the nucleus dorsalis contributes 



