NUCLEUS CARDIACUS NERVl VAGI 123 



smooth muscle. This fundamental difference as to function, 

 which has been proved beyond doubt by the recent investigation 

 of Molhant, had not been clearly recognized; this obscurity was 

 probably favored by the fact that the nucleus ambiguous, to- 

 gether with the motor nuclei of the eleventh, seventh and fifth 

 cranial nerves have often been regarded as visceral, regardless of 

 the fact that their cells cannot be distinguished either histologi- 

 cally or functionally from the cells of the other motor nerves 

 supplying striated muscle. Thus this classification giving undue 

 emphasis to a condition which in mammals no longer exists, has 

 contributed to the general lack of appreciation that the dorsal 

 motor nucleus of the vagus is composed of cells which differ 

 radically both histologically and functionally from those of the 

 nuclei supplying striated muscle, regardless of whether the stri- 

 ated muscle be of somatic or of visceral origin. The name 

 ''dorsal motor nucleus" does not indicate the true function of 

 this cell group, and I shall use the name "sympathetic or vis- 

 ceral nucleus of the vagus." 



The location and extent of the sympathetic nucleus of the 

 vagus is well known and will not be considered in this paper, 

 except to call attention to the fact that it extends as a long 

 column of cells dorso-lateral to the hypoglossus nucleus from the 

 lowest portion of the medulla to almost the level of the oral 

 pole of the inferior olive. An excellent description of the loca- 

 tion of this nucleus is given in Jacobsohn's monograph. The 

 oral portion of the nucleus is composed .of small cells of the type 

 shown in figure 2; this is true both in the case of the lemur and 

 the monkey. As one follows the nucleus caudally a second type 

 of cell begins to appear (fig. 1). The portion of the nucleus in 

 which both types of cells occur is at the level of the oral portion 

 of the hypoglossus nucleus, and here the sympathetic nucleus 

 attains its greatest diameter. The cells of each type are partly 

 separated from each other, although no sharp line of separation 

 is evident. In the lemur the large cells (fig. 1) form a fairly 

 compact group dorsal from the small cells, whereas in the mon- 

 key their relative position is reversed. Proceeding further in a 

 caudal direction, the small cells become rapidly less numerous 



