THE SYMPATHETIC SYSTEM 273 



there are no sensory vegetative tracts, viscero-sensory in 

 particular, in other words, afferent vegetative tracts. 

 These tracts exist, but they are no different from those 

 of the animal system and one is led to conclude, that only 

 in a certain measure does the motor stimulant part of the 

 nervous system of the vegetative life, distinguish itself 

 anatomically from the corresponding part of the system 

 of animal life. 



Let us now follow the sensory vegetative fibres. These 

 fibres coming from the viscera and vegetative tissues in 

 general, reach, after following the general course of the 

 motor tracts, the spinal ganglion and from there, divide 

 themselves, as do the sensory fibres of the voluntary 

 system; that is, there are direct segmentary tracts, tracts 

 which will connect with the motor, central vegetative 

 cells (this is the road taken by the impulse of the 

 unisegmentary vegetative reflex) ; and there are also pluri- 

 segmentary tracts as in the voluntary system (tracts 

 which are the cause of vegetative reflexes in different 

 planes) and long tracts which reach the superior centres 

 of the animal system. 



In this distribution of the pluri-segmentary and long 

 tracts, a group of cells of the posterior horn play an 

 important part, these are part of the cells of the column of 

 Stitting-Clarke; it is apparently the group of cells which 

 play the part of sensory distributors, as the neighboring 

 cells of this same group play the parts in the territory of 

 animal life. 



With the study of the sensory tracts of the vegetative 

 system and their axis nerve centres, we have completed 

 the description of the unit composing the vegetative arc. 

 We have analyzed the parts; let us now, following a logical 

 sequence, study the details of these systems. 



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