HISTOLOGY. 79 



terior roots. From the lateral horn emerge the motor 

 nerve axis-cylinders, the same as in the anterior horn. 

 The nerve cells of the anterior horn resemble a -straight- 

 ened comma, with a very long tail. The reticular 

 processes, column of Clark, and the substantia gelatin- 

 osa, enter the structure of the posterior horn. The 

 substantia gelatinosa covers the horn and surrounds 

 the central canal. The nerves of the anterior horn and 

 the column o>f Clark are very large and stellate. The 

 blood vessels of the cord enter it mostly from the pia 

 mater, and branch repeatedly to form capillaries, which 

 run parallel with the fibers in the wihite matter, but 

 form a net work in the gray matter. In both cases, 

 they are surrounded by neuroglia tissue. There are 

 thirty-one pairs of nerves springing from the spinal 

 cord. The motor nerves are anterior, while the sen- 

 sory nerves are posterior. They are distributed to the 

 skin and other parts of the body, and terminate in a 

 special nerve-ending. 



Exercise No. 46. Make a T. $. of the spinal cord. 



Tcchnic: Mullers fluid, paraffine, haematoxylon and 

 eosin. 



Locate the following: (L. P.) Enclosing mem- 

 branes, median fissures, gray matter, white matter, 

 axis-cylinders in the white matter, T. S. with their en- 



