THE GUSTATORY RELAY IN THE MEDULLA 383 



sented. In addition, the body surface, including hind and fore limbs, 

 body trunk, as well as face and vibrissae area, are laid out in a somato- 

 topically regular manner. The mouth sensitive areas were found not only 

 in loci corresponding to the Vth nucleus but also in the sohtary fasciculus 

 and its nucleus. Tongue tactile responses were observed even more 

 caudally, as far back as the level of the obex in other preparations but they 

 were aroused only by homolateral stimulations. Taste responses from the 

 anterior tongue stimulation were never observed this far caudally. 



In comparing the figurine maps with their counterpart histological 

 reconstructions, it should be noted that the former were drawn according 

 to measurements on the micromanipulator during the experiment while 

 the latter were drawn according to two different criteria. The medio- 

 lateral placement of the tracks within each of the drawings is based solely 

 upon their relative positions as measured in the stained sections. The 

 dorso-ventral dimensions were set up according to the relative depth 

 below the surface at which responses were first recorded, extending for a 

 distance equal to the depth through which they continued to be evoked. 

 Thus, the line corresponding to the electrode path shows only the extent 

 which yielded electrical activity. The two sets of dimensions would agree 

 except for brain shrinkage after fixation and settling of the exposed brain 

 during the course of experimentation. 



Responses from the anterior face, eye, incisors, lips, and mucosa were 

 obtained from the spinal nuclear complex of the trigeminal nerve. Res- 

 ponsive penetrations were found to extend into the region of the reticular 

 formation medial and ventral to the spinal nucleus of the Vth nerve. 

 Gordon et al. (1961) and Wall and Taub (1962) have made similar 

 observations in the cat although the latter believe that the cells are not 

 primary but second order. If so, they do not have the extremely diffuse 

 character of other bulbar reticular neurones, for they are aroused only by 

 sensory stimulation of the head region. 



The bulbar gustatory loci in the present experiment fall within the 

 general boundaries of the anterior tongue taste area described by 

 Pfaffmann et al. (1961). The results indicate that the gustatory and thermal 

 responses from the tongue arise from the nucleus of the solitary tract and, 

 in addition, that responses from tactual stimulation of the tongue, incisors, 

 mucosa of the mouth, hps, and jaw also may be recorded from this struc- 

 ture. Although purely taste loci were found, the taste reactive areas often 

 gave tongue tactile responses like those regularly observed in the im- 

 mediately surrounding placements. This is consistent with the anatomical 

 finding that the solitary nucleus receives trigeminal fibers (Kerr, 1961 ; 

 Torvik, 1956). Thus, the anterior solitary nucleus fits in with the somato- 

 topic arrangement of the primarily tactile nuclei of trigeminal medullary 

 components. It appears that the buccal cavity, including its gustatory 



