78 THE NKHVOl s M -TOl AND ITS CONSERVATION 



pre-sure, but it is not impossible to do so, ;in<l the sensory 

 result i< reported to be still a >en-ation of pres.-ure. A 

 better example of perverse excitation is observed \vhena 

 spot j)revionsly found to bo affected by cold is touched with 

 a rod which i> quite hot. The spot is found to respond with 

 the only sensation which can possibly result from its 

 stimulation, namely, that of cold. So when any area large 

 enough to include both warm and cold spots is brought 

 into contact with something hot, the sensation has a 

 mixed character and may be discovered to contain recog- 

 ni/able elements of warmth and cold. Indeed, the tingle 

 which we call "cold" may be so prominent that for a 

 moment we think that the object has a low instead of a 

 high temperature. 



All the afferent fibers from the skin are gat here* 1 into tin- 

 many small nerves which are found in all parts of the body. 

 and these in their turn unite with others until the total 

 number of the trunks is small and their average size con- 

 siderable. In these larger nerves, as has been said before, 

 efferent as well as afferent fibers are present. If we ex- 

 clude for the moment the afferent nerves of the head, we 

 shall find the remaining fibers of this description parting 

 from their efferent fellows when the cord is closely ap- 

 proached and forming the dorsal roots as they pass in 

 between the vertebrae. Upon these roots there are ob- 

 served to be enlargements, the dorsal root ganglia, and 

 microscopic study shows that these contain the peri- 

 karya connected with the fibers passing through. A- 

 slated in Chapter III, these are of an oval outline, are 

 situated on side branches from their respective fibers, and 

 they are not provided with the ordinary short, branching 

 (lend rites. 



Before the division into dorsal and ventral root> i- 

 reached the afferent libers from the Hirface of the body will 

 have been joined by a -mailer but still immense number 

 from deeper region.-. Some at tent ion must shortly be given 

 to fibers of thi> class. It is evident that the -limiili to 

 which they are subject must be chiefly internal rather 



