488 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



conditions, may lead to a fatal issue, the infiltration throttling, 

 as it were, the paths to and from organs through which life is 

 sustained. When we consider the small relative size of the 

 fourth ventricle, and the fact that the so-called "vital knot" 

 is located in an area which may be computed only by a few 

 millimeters; when we furthermore recognize that such an 

 injury would thus include the vagal, spinal accessory, glosso- 

 pharyngeal, and hypoglossal within its radius of morbid in- 

 fluence, death as an injury to the spot becomes a normal con- 

 sequence. The heart and the entire respiratory system to 

 refer only to those directly concerned with life's processes 

 are the mechanisms first functionally arrested. 



And yet while obstruction of these few square millimeters 

 of bulbar elements will rapidly destroy life, it is possible, says 

 Professor Foster, in the case of some animals "to remove the 

 cerebral hemispheres and to keep the animal not only alive, 

 but in good health for a long time days, weeks, or even months 

 after the operation!" 



There must prevail in this connection, however, another 

 contradictory interpretation of experimental phenomena. In- 

 deed, how can we reconcile the presence of motor centers in 

 the cerebral cortex with the ability of an animal from which 

 both hemispheres have been removed to execute the motions 

 ascribed to these areas? That an animal deprived of its 

 hemispheres will do this is graphically shown in the following 

 lines of Professor Foster's: "We may, perhaps, broadly de- 

 scribe the behavior of a frog from which the cerebral hemi- 

 spheres only have been removed by saying that such an animal, 

 though exhibiting no spontaneous movements, can by the ap- 

 plication of appropriate stimuli be induced to perform all, or 

 nearly all, the movements which an entire frog is capable of 

 executing. It can be made to swim, to leap, and to crawl. 

 Left to itself, it assumes what may be called the natural 

 posture of a frog, with the forelimbs erect, and the hind-limbs 

 flexed, so that the line of the body makes an angle with the 

 surface on which it is resting. When placed on its back, it 

 immediately regains its natural posture. When placed on a 

 board, it does not fall from the board when the latter is 

 tilted up so as to displace the animal's center of gravity; it 



