No. 389.] REVIEWS OF RECENT LITERATURE. 435 
it open to sensory stimulation? and, thirdly, what part of the central 
nervous system is essential to this state? Answers to these ques- 
tions are obtained from observations on guinea pigs, hens, frogs, and 
asps. 
The postures which the “hypnotized’’ animals assume represent 
usually some step in the process of recovering from their abnormal 
positions, and they are held in these positions by a tonic contraction 
of their muscles. They are, so to speak, like so many instantaneous 
photographs of animals, in process of righting themselves. Verworn 
believes that the reason they remain motionless in this condition is 
not because their motor impulses have been inhibited, but simply 
because there are no such impulses. 
In the “hypnotic” condition the animals’ senses are normally 
acute, but their reflex capabilities are probably actually reduced, 
though the loss of this power may in part be due to exhaustion. 
Heubel found that the experiments made on the frog could be 
performed as well on an animal without its cerebral hemispheres as 
on one in normal condition. This important observation has been 
confirmed by Danilewsky and by Verworn, and the latter has demon- 
strated the same to be true for the hen. In the hen, however, the 
presence or absence of the cerebrum makes a difference. While in 
both cases the animals may be brought into a motionless condition, 
a hen without a cerebrum will remain motionless an hour or more, 
instead of ten minutes, as in the normal animal. Moreover, her 
recovery is always associated with some obvious sensory stimulation, 
which is not necessarily so in the case of the normal hen. Guinea 
pigs whose spinal cords have been cut respond to the assumed hyp- 
notic influence only by the anterior portions of their bodies. From 
these experiments Verworn concludes that the center for readjusting 
the position of the body, as well as that for the tonic contraction of 
the muscles, cannot lie in either cerebrum or cord, but must be some- 
where between these parts. He assumes with reason that it is located 
in the cerebellum. It is remarkable, however, that Verworn has not 
attempted to test this assumption by trying experiments on animals 
from which the cerebellum had been removed. 
According to Verworn the motionless condition of the animals is 
dependent upon two factors—a tonic stimulation of the cerebellar 
reflex center, whereby the animal is held in an attitude of recovery, 
and an inhibition of the motor areas of the cerebrum. As the cere- 
brum acts only in this negative way, an animal without its cerebrum 
may be made motionless by the positive action of its cerebellar cen- 
. 
