710 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



neither attracted nor repelled, save in so far as the selection of the points toward 

 which it will fly is an example of attraction. Sexual and maternal reactions 

 both disappear, and neither fear nor desire is evident. 



In ascending the mammalian series the removal of the cerebrum becomes a 

 matter of increasing difficulty. The reasons for this are several, and reside in 

 the increasing size of the blood-vessels and the nutritive complications depend- 

 ent on the increase in the mass of the cerebrum, as well as in the greater physi- 

 ological importance of this division. Goltz l has been able by repeated ope- 

 rations to remove the entire cerebrum of a dog, and still to keep the animal 

 alive and under observation for eighteen months, at the end of which time the 

 animal, though in good health, was killed for further examination. This dog 

 was blind, though he blinked when a bull's-eye lantern was suddenly flashed 

 in his face. He could be awakened by a loud sound, and when awake re- 

 sponded to such sounds when intense by shaking the head or ears. This 

 would not, however, be complete proof that he could hear. The sense of taste 

 was so far present that meat soaked in quinine was rejected after tasting. 

 Tactile stimuli and those involving the muscle sense, as in the case when the 

 animal was lifted, caused him to struggle and to bite in the direction of the 

 irritation. These reactions were modified according to the locality of the stim- 

 ulus. The power to make movements expressive of pain was still present. 



On the motor side the dog was capable of such highly complicated acts as 

 walking, standing, and eating, and in these operations was guided by the muscle 

 sense and that of contact. The sexual instincts were lost, but the animal was 

 excessively active, and became more and more excited when ready to defecate 

 or when hungry. 



The examination of the brain showed that all parts in front of the mid- 

 brain had been removed or were degenerated, so that the defects were due to a 

 removal of rather more than the cerebrum proper. 



Emotions, feelings, conscious sensations, or the capacity to learn were entirely 

 wanting in this dog, and its reactions were those of a very elaborate machine. 



If we compare, now, the effects of the removal of the cerebral hemisphere 

 in the bony fish, the pigeon, and the dog, we see that the results of the operation 

 are progressively more disturbing as we pass up the series. In the higher 

 animals the effects are more often fatal, the disturbance immediately following 

 is much more severe, the return of function slower, and the permanent loss 

 greater. As a partial exception to the above statements is the observation that 

 after operation the general health of pigeons always declines, and it is not 

 possible to keep them alive more than about six weeks. On the contrary, a 

 dog could be kept in good health for some eighteen months ; but there is this 

 difference, that the removal in the case of the dog was made by several suc- 

 cessive operations. 



By removal of the cerebrum the higher animal tends to lose just those 

 capacities which best serve to distinguish it from the lower forms. When, 

 therefore, the inquiry is made why the results gotten in the dog are not obtain- 

 1 Archiv fur die gesammte Physiologic, Bd. xli. 



