SYSTEMATIC SYNTHESIS OF TISSUES INTO ORGANS. 277 



Spinal Ganglia. 



673. THE SPINAL COED is CONSTRUCTED of an exter- 

 nal sheath, the surface of which is a continuation of the 

 arachnoid of the under surface of the Brain. Adjoin- 

 ing this is found a continuation of the subarachnoidean 

 areolar texture, filled with the same fluid as that of the 

 Brain, next to which is a continuation of the pia mater. 

 In other words, the spinal cord is but a prolongation of 

 the lower portion of the Brain, which is an enlargement 

 of the cord. 



674. THE SPINAL CORD is CONSTRUCTED INTERNALLY 

 of white tissue enclosing gray, the latter, when cut across, 

 showing the form of a quarter moon, the horns being 

 near the surface of the cord, where the nerves enter or 

 leave, thus dividing the cord on each side into three 

 parts, called the front, middle, and back columns, while 

 two grooves at the centre of the front and back face of 

 the cord indicate the line of its division into its right and 

 left halves, or right and left cords. 



675. THE GRAY CENTRAL PART OF THE CORD CON- 

 TAINS millions of cells, with some of which only the 

 white fibres that enter and leave are connected : other 

 cells are connected with white fibres that enter and 

 leave, and also with those extending up to the cranial 

 ganglia, while others again are connected with fibres 

 that either enter or leave, and with those that extend to 

 other cells in the cord or in the Brains. 



676. THE WHITE PART OP THE CORD contains some 

 fibres that extend to or from the Brain, and some that 

 extend to cells in the cord, and some that extend be- 

 tween cells of the cord. 



677. ON ALL THE FIBRES CONNECTED WITH THE BACK 



PART OF THE CORD there is found, a short distance from 

 the cord, but within the canal, a small quantity of gray 



673. How ? 674. How ? 675. What does ? 676. What said of ? 

 677. What found-? 



