444 



TEXT-BOOK OF PHYSIOLOGY. 



Structure of the Gray Matter. The gray matter is arranged 

 in the form of two crescents, united in the median line by a trans- 

 verse band or commissure forming a figure resembling the letter H. 

 Though varying in shape in different regions of the cord, the gray 

 matter in all situations presents on either side an anterior or ventral 



Superior or Cervical Segment 

 of Spinal Cord. 



Middle or Dorsal Portion Inferior Portion of Cord and 

 of Cord. Cauda Equina. 



FIG. 203. SUPERIOR, MIDDLE, AND INFERIOR PORTIONS OF SPINAL CORD. 

 i. Floor of fourth ventricle. 2. Superior cerebellar peduncle. 3. Middle cerebellar 

 peduncle. 4. Inferior cerebellar peduncle. 5. Enlargement at upper extremity 

 of postero-median column. 6. Glosso-pharyngeal nerve. 7. Vagus. 8. Spinal 

 accessory. 9, 9, 9, q. Ligamentum denticulatum. 10, 10, 10, 10. Posterior roots 

 of spinal nerves, n, n, n, n. Postero-lateral fissure. 12, 12, 12, 12. Ganglia 

 of posterior roots. 13, 13. Anterior roots. 14. Division of united roots into 

 anterior and posterior nerves. 15. Terminal extremity of cord. 16, 16. Filum 

 terminate. 17, 17. Cauda equina. I, VIII. Cervical nerves. I, XII. Dorsal 

 nerves. I, V. Lumbar nerves. I, V. Sacral nerves. (Sappey.} 



and r a^posterior or dorsal horn. Between the two horns there is a 

 portion termed the intermediate gray substance. The commissure 

 presents in its center fr pat-raw fo*fl] yfrjffr f^rtiprw^^pi^bouiihe 

 entire, lp f nytti <q ^heord. This canal is lined by cylindric epithelium 

 and surrounded by gelatinous material. (Fig. 204.) 



