NERVE-TISSUE. 



287 



near the median line. A fourth group of ganglionic elements, 

 constituting the columns of Clarke, is found only in the thoracic 

 portion of the spinal cord, in the foremost part of the posterior 

 horn, near the posterior commissure. In the posterior horn the 

 ganglionic elements are always small, scattered, and with com- 

 paratively few offshoots. The illustration is taken from the 

 third group of the anterior horn. (See Fig. 120.) 



The ganglionic elements are bioplasson formations, which, 

 according to the number of offshoots, are termed unipolar, 



FIG. 120. GANGLIONIC ELEMENTS FROM THE ANTERIOR OR MOTOR 

 HORN OF THE SPINAL CORD OF A CHILD. 



U, unipolar ; JB, bipolar ; T, tripolar ; Q, quadripolar ganglionic element ; G, gray sub- 

 stance, containing small, shining nuclei, and a number of axis-cylinders; CL, capillary 

 blood-vessel, longitudinally, CT, capillary blood-vessel, transversely, cut, each surrounded 

 by the lymph-sheath. Magnified 600 diameters. 



bipolar, tripolar, quadripolar, or multipolar. The number of 

 offshoots is in close relation with the size of the corpuscle. A 

 light space is often found around the ganglionic element j this is 

 the so-called " periganglionic space," which, in all probability, is 

 artificially produced by the shrinkage of the neighboring tissue. 



