Edinger, Comparative Psychology. 441 



in the lizards, and certainly in the birds, a large fiber-tract lead- 

 ing from the nucleus of the trigeminus terminates in a field situated 

 close behind the olfactory apparatus. This field, the lobus par- 

 olfactorius, attains an enormous size in birds and the question 

 arises as to what function this structure can serve. The importance 

 of the beak, which is innervated by the trigeminus, the extraordi- 

 narily rich trigeminal supply about the mouth and in the tongue, 

 and the further circumstance that stimulation of the lobus par- 

 olfactorius produces movements of the beak, lead one to the con- 

 clusion that we have here a center for the territory innervated by 

 the trigeminal nerve, that is, a hitherto quite unknown feature of the 

 brain. I am now engaged, together with Dr. Kappers, in tra- 

 cing out this apparatus and we are able even now to declare that 

 tn all vertebrates up to the mammals there must exist an as yet 

 scarcely studied sense which is localized about the mouth and has 

 its center in the lobus parolfactorius. In the chameleon, with 

 very small olfactory nerves, this lobe is almost as large as in birds, 

 and we should remember that this animal catches its food by 

 extending its tongue. We know how significant in fishes is the 

 investigation of food by means of the barbels and the tip of the 

 snout, how serpents are guided by touching with the tongue, and 

 as we trace these functions, which we may tentatively designate 

 as the oral sense, upwards in the scale we find, not without sur- 

 prise, that even the mammals possess in this same locality a brain 

 structure which is small and atrophied in those whose snout plays 

 no important role (man, the apes, and ruminants), but which 

 becomes a giant structure in mammals, of the most diverse orders, 

 so far as they make extensive use of the snout. In the brains of 

 the hedgehog, the mole, the armadillo, also in swine and the 

 elephant, the lobus parolfactorius is strongly developed. In man 

 it has completely disappeared except for a vestige in the atrophied 

 lamina perforata anterior. So much for the oral sense. It is 

 little enough, yet it shows that sense psychology acquires an 

 entirely new problem from anatomical studies. 



According to the degree of development of the olfactory lobes 

 in mammals much may be inferred as to the condition of the 

 olfactory sense. Since these matters have been well known from 

 the time of Broca, I will now only briefly refer to the fact that 

 these lobes in the lower mammals make up more than half of the 

 entire brain, that in the beasts of prey they play an important 



