218 



TWENTY-FIRST LECTURE. 



entericus, discovered by Auerbach, with its manifoldly mul- 

 tipolar cells (L. Gerlach). The former plexus appears to be 

 of a motory and sensory constitution ; the latter possesses 

 predominantly the former nature. Such small ganglia are 

 also encountered in the urinary and generative organs, as 

 well as in glandular structures. Our Fig. 186, a ganglion 



Fig. 186. — Ganglion from the submucous plexus of the small intestine of an infant ; a. ganglion 

 with the ganglion cells ; b, c, nerve trunk, with the pale, nucleated fibres ; 2, a nerve trunk from a 

 boy five years old. 



from the submucous plexus, may represent this. At a, we 

 perceive the ganglion with the non-medullated, nucleated 

 fibres ; at 2, a similar nerve trunk is isolated. 



Let us now turn to the cerebro-spinal system, to the spinal 

 cord and brain. 



The spinal cord (Fig. 187) presents a cylindrical cord, con- 

 sisting of an inner gray and an outer white substance. Both 

 form connected layers of substance throughout the entire 

 length of the spinal cord. The gray substance forms an 

 irregular Latin H, in transverse sections. One distinguishes 

 accordingly, anterior (d) and posterior (e) horns. The latter 

 are then invested by Rolando's " gelatinous " substance. In 

 the centre of the whole we perceive, lined with cylinder cells, 

 the axis canal (a), the last remains of a much wider cavity 

 in the earlier foetal period. Two deep furrows, the fissura 

 anterior (b) and posterior (c), cut nearly into the centre. In 



