57 



LESSON XV. 



SPINAL, CORD, CEREBELLUM, AND 

 CEREBRUM. 



(a) Spinal Cord with Anterior and Posterior 



Roots. 



A segment of the cervical cord of a cat with the anterior and 

 posterior roots of the two .sides (to a point a short distance beyond 

 their junction) was removed and hardened in mercuric chloride. 

 To insure the hardening of the roots in a plane so that, the cord and 

 roots on both sides might be cut in one section, the following de- 

 vice was made use of: An opening large enough to admit the cord 

 was made in a card; one end of the cord segment was pushed 

 through this opening, and the roots were spread out on the card to 

 which they adhered. The preparation was then placed in mercuric 

 chloride. After hardening it was stained en masse in borax carmine 

 for several days, embedded in paraffin, and sectioned. Fix to the 

 slide, and mount in balsam. 



Study under low power. Observe the anterior and pos- 

 terior roots in connection with the anterior and posterior 

 horns of the gray matter. . Sketch under low power. 



(b) Section of Spinal Cord Stained in Weigert's 



Hsematoxy lin . 



A human cord was hardened in Mailer's fluid, embedded in 

 celloidin, stained in Weigert's hsematoxylin, dehydrated, and 

 cleared in carbol-xylol. Place section on slide, 'wipe away excess of 

 clearing fluid, and mount in balsam. 



Study under low power. The cord is nearly divided 

 into two symmetrical halves by two fissures, the anterior 

 and posterior median fissures, the latter is really only a 

 connective tissue septum. In each half of the cord the 

 gray matter, which in this section, has a yellowish-brown 

 color, appears in the form of a crescent. The convex 

 borders of the two crescents are opposed to each other. 

 The anterior horns of gray matter are broader and shorter, 



