MEDULLA OBLONGATA OF AMBLYSTOMA 371 



a short distance farther forward, at the level where the tractus 

 spino-cerebellaris separates from the tractus spino-bulbaris et 

 tectalis (fig. 20), are neurones which clearly belong to the cere- 

 bellum and which closely resemble those last described. The 

 dendrites of these neurones engage terminals of the sensory root 

 fibers of the cranial nerves and of the tractus spino-bulbaris and 

 spino-cerebellaris systems; they also reach into the motor teg- 

 mentum. The axones are more slender than those of the neurones 

 last described and apparently form part of the tractus cerebello- 

 tegmentalis system. The nature of the terminals of the tractus 

 spino-cerebellaris in this region is shown in figures 19 and 47. 

 The more lateral neurone shown in figure 31 is a type frequently 

 observed in relation with the spinal \ root. This neurone should 

 probably be regarded as belonging to the substantia gelatinosa 

 Rolandi, for its chief dendrites end in relation with fibers of the 

 spinal V root. Yet other dendrites reach the VIII roots, the 

 ascending secondary visceral tract and the motor tegmentum. 

 Figures 26 and 29 illustrate two tangential neurones whose den- 

 drites also effect synaptic relations with the sensory V root fibers. 

 These highly specialized neurones will be considered later in 

 connection with the tegmentum (p. 379). In the vagus region 

 there are interesting neurones whose dendrites connect with both 

 the spinal Y root and the fasciculus solitarius, which will be 

 described immediately. 



I have no observations on the neurones of the second order 

 related to the pref acial fasciculus solitarius, but in the vagus region 

 our Golgi preparations illustrate many of these elements. Figure 

 40 shows an impregnation of several types of neurones. The most 

 dorsal of these belongs in the lobus visceralis dorso-medially of 

 the fasciculus solitarius and its dendrites arborize chiefly within 

 this fasciculus. Numerous axones of these elements are impreg- 

 nated. They are seen to take two divergent courses. Some pass 

 ventro-laterally to enter the ascending secondary visceral tract 

 of the same side ; others pass ventro-medially to enter the ventral 

 commissure, beyond which they cannot be separately followed. 



Other neurones in this preparation lie immediately ventrally of 

 the fasciculus solitarius. Their dendrites are directed chiefly 



