HABIT FORMATION IN THE DOG 3 



were eliminated. That the method itself can be put to prac- 

 tical use and be so improved as to become wholly reliable 

 has not yet been demonstrated. In any case there remains the 

 question whether the results obtained by this method would 

 show the relative importance of the animal's sensitivity to 

 given stimuli, as referred to his behavior under normal condi- 

 tions. A change in the auditory stimulus great enough to occa- 

 sion change in the saliva-reflex conditioned by it may be much 

 too slight to occasion a change in the so-called voluntar}^ reac- 

 tions ; or the contrary may be true. 



In 1 891, Goltz^ removed the entire cerebrum from one 

 dog, which lived for over eighteen months thereafter under 

 constant observation in the laboratory. At very high tones or 

 at very loud noises the animal would prick its ears or turn its 

 head. If the stimulus was very intense it would even strike at 

 its ear with the forefoot "as if it wished to stop its ear." From 

 these reactions, Goltz denied that the animal was "totally 

 deaf." Munk calls attention to the possibility that the animal 

 was reacting to pain-stimuli and not to tone or even to noise. 

 This suspicion seems to be well grounded. 



Munk* himself made some experiments with dogs, using 

 nine pipe -organ tones about an octave apart, and taking the 

 animals' ear-, head- and body -movements as criteria of audi- 

 tion. If these movements were no longer made after operation 

 on the cerebrum, he assumed that deafness has been produced. 

 Having extii-pated different regions of the supposed auditory 

 center from trained dogs, and having compared the motor reac- 

 tions following the operation with the former responses of the 

 dogs, Munk concluded that the dog's center for tone lies in the 

 temporal lobe; that perception of the high tones is conditioned 

 by the function of the anterior portion of the center, while that 

 of the deeper tones depends on the activity of the posterior 

 region. While these results are extremely interesting, and val- 

 uable if it can be established that the animals reacted only to 

 auditory stimuli, yet the behavior method is open to the criti- 

 cism that it cannot be used to determine the animal's discrim. 

 ination between stimuli. Kalischer, whose work we shall pres_ 



^ Described by Munk, H. Functionen von Hirn und Ruckenmark. Berlin, 

 1909. Article Ueber den Hund ohne Grosshirn. 1894. Pp. 1.37 ff. 



" Munk, H. Ueber die Functionen der Grosshirnrinde. Berlin, 1890. Pp. 

 113 ff. 



