148 THE BRAIN OF THE TIGER SALAMANDER 



there are also innumerable taste buds which are innervated by fibers 

 which enter the f . solitarius. The general chemical sensibility is pre- 

 served if the taste buds are denervated, but the specific gustatory 

 function of the taste buds is lost if the general cutaneous innervation 

 of the surrounding skin is eliminated. A similar relation prevails with 

 taste buds within the mouth, for these have a double innervation; 

 and in man the gustatory function is abolished if the trigeminal in- 

 nervation of the tongue is surgically destroyed, even though the 

 specific innervation of the buds remains uninjured; this loss, how- 

 ever, is temporary, and after a few weeks gustatory function returns 

 (Gushing, '03). 



Amblystoma has no cutaneous taste buds, but the mouth cavity is 

 abundantly supplied with them. They are especially numerous on the 

 palate among the vomerine teeth, and these buds have a peculiar 

 accessory innervation — a compact skein of circumgemmal fibers of 

 uncertain origin ('256; Estable, '24). These fibers separate from a 

 plexus related with the ramus palatinus and may be derived from a 

 trigeminal anastomosis; but this has not been demonstrated. 



The tactile, general chemical, and gustatory systems are as inti- 

 mately related centrally as they are peripherally. All taste buds of 

 all animals, wherever found, are supplied by fibers which discharge 

 centrally into the nucleus of the f. solitarius or its derivatives. In 

 those fishes which have cutaneous taste buds with exteroceptive 

 functions the central connections of these buds differ from those of 

 buds within the mouth which have interoceptive functions. These 

 details need not be given here ; the interested reader is referred to a 

 recent paper ('446) and references there given. These differences are 

 explained by the fact that stimulation of interoceptive taste buds 

 evokes visceral responses, but excitation of exteroceptive buds is fol- 

 lowed by somatic movements for capture of food. 



In Amblystoma, as in man and all other vertebrates, all fibers from 

 taste buds enter the f . solitarius. Most fibers of all modalities of gen- 

 eral cutaneous sensibility of the head enter the sensory V nucleus; 

 but a small number of them pass through this nucleus to enter the 

 f . solitarius, thus providing for integration of general somatic sensory 

 and gustatory sensibility. The prefacial f. solitarius carries gustatory 

 impulses forward into the neuropil of the superior trigeminal nucleus 

 in the auricle. A third and much more extensive provision for bring- 

 ing general cutaneous and both general and special visceral sensi- 



