MEDULLA OBLONGATA OF AMBLYSTOMA 



409 



27 



Fig. 25 Transverse section at the level of the V roots, illustrating the relations 

 of neurones of the eminentia trigemini {em. F.) to both the V roots and the tractus 

 spino-bulbaris (/r.sp. 6.). Golgi method. X 100. 



Fig. 26 Transverse section immediately caudad of the V roots, showing incom- 

 plete impregnations of one small neurone of the sensorj- V nucleus (em.V.) and a 

 tangential neurone of the marginal zone of the gray substance whose dendrites are 

 directed toward the area acustico-lateralis, the sensory V root and the tegmentum. 

 On the opposite side of this section and in adjacent sections larger neurones of the 

 eminentia trigemini send dendrites into the sensory V root and the entire tegmen- 

 tum, particularly the regions of the tractus spino-bulbaris and the bulbar lemnis- 

 cus. Golgi method. X 100. 



Fig. 27 Transverse section immediately in front of the VII roots. Golgi 

 method. X 100. One neurone of the area acustico-lateralis is partially impreg- 

 nated. Its axon arises from the ventral dendrite and extends toward the ventral 

 commissure. The dendrites reach the VIII and V roots and the secondary visceral 

 tractitr.v.a.). Two small neurones of the tegmentum (formatio reticularistype) 

 are also impregnated, their axones being directed into the ventral commissure and 

 their dendrites into the tegmentum and secondary visceral tract. These small 

 neurones probably discharge into the motor VII nucleus of the same and the 

 opposite side. The big ventral neurone lies within the area of the motor VII 

 nucleus, but since its axon is not impregnated it is impossible to determine 

 whether it belongs to this nucleus or to the motor tegmentum. Most of its den- 

 drites pass caudad out of the plane of the section. The adjacent section shows 

 them spreading ventrally and laterally throughoilt the entire tegmental area. 

 Farther caudad in this series some dendrites of a similar neurone reach laterally 

 as far as the spinal V root. 



THE JOURNAL OF COMPARATIVE NEDROI.OGY. VOL. 24. NO. 4 



