188 



PRACTICAL MICROSCOPY. 



3. Subdivisions of the gray substance, (a) The central canal. 



(Should the section have been taken from the extreme lower cervical 

 cord, this canal as such will be difficult of demonstration, a number 

 of deeply stained cells only remaining.) (b) The gray commissure, 

 anterior and posterior, (c) The gray columns, (d) The anterior 

 gray cornua, broad and not reaching the periphery of the cord sec- 

 tion, (e) The posterior cornua, narrow and passing completely out, 

 posteriorly, to form the posterior root of a spinal nerve. 



FIG. 122. TRANSVERSE SECTION OF THE SPINAL CORD. MIDDLE CERVICAL REGION. X 60. 



A. Anterior. B. Posterior. 



The references in Fig. 131 apply also to this illustration. Also vide text. 

 This section was made from the cord of a man who died at the age of 75 years, from senile 

 dementia. The gray substance is perfectly normal, but of somewhat diminished area. 



(H.) 



4. The white substance (select a field, e. g., in the anterior 

 median column, and observe the transversely divided nerves), (a) 

 The nerves are not collected into fasciculae, but each fibre pursues 

 an independent course, (b) The axis cylinders, stained lightly 

 with the eosin. (Note the great variation in size. ) (c) Most of the 

 axis cylinders surrounded by more or less concentric rings of translu- 



