The Internal Senses. 699 



The most notable difference between the brain of man and the brains 

 of the other mammalia, is in man's greatly superior development of the 

 frontal lobes of the hemispheres, prefrontal and postfrontal. There is 

 also a greatly superior development of the posterior lobes. As shown 

 by the experiments of the pl^siologists, the mastoid (middle) lobe is 

 nearly all accounted for as being occupied by centers of direct sensation 

 and motion, but when the frontal convolutions of monkeys and dogs 

 have been destroyed, they show signs of great mental deterioration. 

 Monkeys lose their interest and curiosity in their surroundings, and their 

 faculty for intelligent observation. In the case of dogs deprived of the 

 frontal regions of their hemispheres, they lose their memory, and are 

 governed in their actions chiefly by the sensory stimulation of the mo- 

 ment. According to Goltz, they are irritable and restless. They can 

 still smell, hear, taste and see, but their expression is stupid, and they 

 are unable to steadily inspect anything, or fix the attention. " If a bone 

 is thrown to the animal at some distance, it runs to it with great alac- 

 rity, but does not have the sense to stop at the right moment and sink 

 its head, so that it runs beyond the mark. Instead, however, of turn- 

 ing round and looking for the bone in a methodical 'way, the animal ap- 

 pears to forget what it was after, and runs on regardlessly until the bone 

 is lifted, and the animal's attention again attracted to it. " They will 

 eat meat thrown to them, as long as it remains in sight, but if they 

 happen to lose it, will not look for it, and seem to forget they had it. 



Ferrier's experiments go to show that the frontal regions contain the 

 cerebral motor centers for the head and eyes. When these parts of the 

 brain have been destroyed, there has followed degeneration of motor 

 fibres leading downward through the internal capsule and foot of the 

 crus cerebri as far as the pons varolii. The fibres of the anterior pyra- 

 mids were not affected, so that the motor connections of these degen- 

 erated fibres belonged to the head and eyes, and not the limbs. It 

 would be absurd, however, to maintain that the frontal regions contain, 

 at least in the dog, monkey and man, nothing but the motor centers for 

 the mDvemeuts of the head and eyes, and that the great advance in this 

 part of the brain of man, simply gives him greater facility and com- 

 mand of these parts. It does that, no doubt, but it does much more. 

 Around these centers of motion lie, without doubt, those ganglia in 

 which are co-ordinated those stages of stimulation which are preliminary 

 to a final discharge in setting up the activities of those motor centers. 

 The motions of the head and e} r es are not so very numerous or compli- 

 cated, and in man not so very much more so than in the monkey ; but 

 the purposes, motives, and varieties of stimulations which may lie be- 

 hind these motor performances, may be practical^ infinite. Where the 

 motives are but few, confined, as in the dog, cat, &c. , to matters of 



