1 3 6 THE IN VOL UNTAR Y NER VO US S YSTEM 



concerns the connexion of central nerve cells with peripheral 

 motor cells ; in the thoracic region we were considering not the 

 enteral but the sympathetic muscular system as far as concerns 

 the connexion of central nerve cells with peripheral motor cells. 

 It does not therefore follow that the nucleus intercalatus of 

 Staderini, which constitutes the connector neurons of the enteral 

 nervous system in the medulla, is strictly a continuation of the 

 intermedio-lateral cell column in the thoracic region, which forms 

 the connector neurons belonging to the sympathetic nervous sys- 

 tem. The former cell group would be more strictly comparable 

 to the connector neurons in the sacral region, which give origin 

 to the connector fibres forming the pelvic nerves. At present 

 we have not sufficient experimental evidence to enable us to 

 speak accurately of the position of these sacral connector 

 neurons. 



On the other hand, if we take into consideration not only 

 the motor cells which send motor fibres to the endodermal 

 muscles but also the cells which send inhibitory fibres to those 

 muscles, these cells belong mainly to the sympathetic system and 

 the cells of their connector neurons are presumably situated in 

 the intermedio-lateral cell group. I am inclined on the whole to 

 look upon the primary connector neurons of the involuntary 

 nervous system as forming a cell column of the same nature as the 

 cell column of the lateral horn, just as I look upon the corre- 

 sponding connector neurons of the voluntary nervous system as 

 all derived from the cells of the posterior horn. 



The evidence points to the following conclusions : 



1 . The cells on the floor of the fourth ventricle, known as 

 the dorsal nucleus of the vagus, are all connector cells belonging 

 to the splanchnic segmentation and include those belonging to 

 the involuntary as well as the voluntary nervous system. 



2. The small-celled part (the nucleus intercalatus of Staderini) 

 gives origin to the connector nerves of the involuntary nervous 

 system, and the large-celled part with its continuation into the 

 spinal cord in connexion with the sensory fibres of the fasciculus 

 solitarius gives origin to connector fibres of the voluntary nervous 

 system. 



3. I conclude that these two sets of connector neurons enable 

 primary or segmental reflexes to be carried out both in the in- 

 voluntary and voluntary splanchnic segments. At the same time, 



