Hardesty, Medulla Spinalis of the Elephant. 137 



which had been removed in company with the head and conse- 

 quently unexamined by him. 



It should be mentioned that the segments cephalad to cer- 

 vical V were more flattened, i. e., the lateral diameter exceeded 

 the dorso-v-entral to a greater extent than that of any of the suc- 

 ceeding segments. There was nothing to show that this flat- 

 ness was not normal. It will be subsequently seen that this 

 feature is also well-marked in the horse. 



Fig. I, plate IX is an outline sketch constructed from the 

 subjoined pieces. Its dimensions were controlled by actual 

 measurements. It shows the relative size of the different seg- 

 ments comprised as well as the transition of the medulla ob- 

 longata into the medulla spinalis. The transverse lines indicate 

 the levels at which the diameters were measured for Table I. 

 The levels from which the sections were taken which were used 

 for the illustrations of the internal structure of the specimen, 

 are indicated by the number of the figure showing the sections. 

 The medulla oblongata at the level of the caudal extremity of 

 the ventriculus quartus (calamus scriptorius) and involving the 

 decussatio lemniscorum and a portion of the nuclei giving ori- 

 gin to the lemniscus (Fig. 2. plate X) had a lateral diameter of 40 

 mm. Its greatest dorso-ventral diameter was 23 mm. However, 

 when taken from the floor of ventriculus quartus the dorso-ventral 

 diameter was only 18 mm. At the level of the decusssatio 

 pyramidum (Fig. 4, plate XI) the lateral diameter was 34 mm. 

 and the dorso-ventral 17 mm. These measurements show that 

 the inferior portion of the medulla oblongata is also considera- 

 bly flattened laterally. Kopsch's measurements indicate that 

 this feature is maintained, but to a less marked degree, through- 

 out the remainder of the specimen. In the thoracic region the 

 lateral diameter exceeds the dorso-ventral never less than 4 mm., 

 and in the intumescentia lumbalis this excess is even as much 

 as 9 mm. It will be remembered that in the mammals more 

 commonly studied, dog, cat, rabbit, rat, man, monkey, gorilla 

 and orang-outang, an excess of the lateral diameter over the 

 dorso-ventral is marked to a noticeable extent only in the intume- 

 scentia cervicalis. Even here for some members of the group, 



