80 PEARL BRIGGS BULLARD 



t 



OBSERVATIONS 



Common structures 



In glancing over the drawings, one of the first things which 

 attracts attention is the marked similarity of form throughout 

 the series. Each cord is possessed of bilateral symmetry and 

 presents a grey figure in the shape of the letter H, at times con- 

 siderably modified. Each half of the grey figure of the cord has 

 the ventral and dorsal horn, the gelatinous substance of Ro- 

 lando being found at the apex of the latter. The two sides of 

 the grey figures are connected by a commissure in which is- a 

 central canal surrounded by a homogeneous substance (central 

 gelatinous substance) similar in structure to the gelatinous sub- 

 stance of Rolando. The white substance surrounding the grey 

 is divided into a dorsal and a ventro-lateral funiculus by the 

 more or less well marked dorso-lateral sulcus, the line of 

 ingrowth of the dorsal root. The dorso-intermediate sulcus pro- 

 vides an interesting comparison which will be mentioned when 

 the dorsal funiculus is considered. Each section shows a ventral 

 median fissure but not all, in Weigert sections at least, presents 

 a dorsal median septum. The reticular formation, present in 

 all, varies considerably in amount as the drawings show. 



Diameters 



Text-books on neurology state that the human spinal cord in 

 each region has a lateral diameter greater than the dorso-ventral. 

 Authorities agree that the greatest difference in these diameters, 

 or in other words, the portion of the cord most flattened dorso- 

 ventrally, is the cervical region. Cunningham '09) states that 

 the lumbar region is more nearly circular than the thoracic. 

 Piersol ('10) on the other hand, gives the lumbar region as being 

 more flattened than the thoracic. The measurements for man 

 here given agree with those of Cunningham. However measure- 

 ments taken from several other specimens in this laboratory agree 

 more nearly with Piersol. 



From table 5, which records in the form of a ratio the relative 

 amount of flattening in each region, it is seen that the bat has a 



