82 PEARL BRIGGS BULLARD 



possess greater flattening in the thoracic than in the cervical 

 region, the sections of which latter are approximately circular. 

 Man, bear, and rhesus monkey stand alone in having a cord in 

 which the thoracic region possesses more dorso-ventral flattening 

 than does the lumbar region. 



In about half the mammals of the series, including man, the 

 cervical region of the cords shows a greater dorso-ventral flat- 

 tening than the lumbar region. In the other half the order is 

 reversed, the greater flattening occurring not in the cervical but 

 in the lumbar region. Chief among this latter number are the 

 sheep, rabbit, hog and Java monkey which, as will be noted, 

 have relatively a very small dorsal funiculus. While on the other 

 hand the bat, mouse, and man have greatlj^ flattened cervical 

 regions and very large dorsal funiculi (column 4, table 8b). The 

 shape of the cords in the series varies to such an extent in each 

 region that it is difficult to say that any given cord is of a pre- 

 dominately rounded or flattened form throughout its length. 

 However, from data here given we may say the bat and elephant 

 are types of dorso-ventrall}^ flattened cords while the fox pos- 

 sesses a cord of rounded form. 



Enlargements and total area • 



As is well knoAvn the cervical and lumbar enlargements are 

 the result of a response to the increased demand for innervation 

 made by the extremities. Furthermore, four-footed animals 

 with approximately equally developed extremities have the area 

 of the cervical enlargement greater than that of the lumbar, 

 due largely to the fact that the cervical region is concerned with 

 the innervation of the tissues of the thorax in addition to those 

 of the upper extremity as well as to the fact that this region 

 carries all the fibers connecting the regions below it with the 

 brain. The kangaroo, with its very small anterior extremities, 

 has a lumbar enlargement the total area of which in transverse 

 section is 13.99 sq. mm. greater than the total area of the section 

 of its cervical enlargement (column 1, table 6, and fig. 8, C and 

 L). 



