953 
once that they make use of their eyes and that the optic “Stellreflexe” 
reveal themselves after the fixing of the surrounding objects. On 
examination of such animals without labyrinths, blindfolded or not, 
the “Stellreflexe” can be made to appear or to disappear at will. 
The fact that the optic ‘“Stellreflexe” react only in animals with 
unimpaired cerebrum, points to a correlation of the optic “Stellreflexe” 
with the presence of the cortex. This follows as a matter of fact, 
since dogs and cats deprived of their cerebrum, do not show optic 
reactions, except the pupillary reflex and the closing of the eyelids 
on exposure to light. 
It is interesting to observe the contrast between the dog and the 
cat on the one side and the rabbit on the other. The normal rabbit 
with cerebrum has no optie “Stellreflexe’”’, and as regards “Stellreflexe”’, 
does, therefore, not differ from a so-called Thalamus-rabbit. The 
apparatus essential in the rabbit for standing and for posture, is, 
indeed restricted to the brain-stem; in dogs and cats connections 
with the cortex, probably with the optic cortex, as the experiments 
have proved, also come into account. Special experiments are needed, 
of course, to ascertain whether the mere cirumstance of the optic 
cortex being intact, is sufficient for the optic “Stellreflexe” to present 
themselves. 
The fact that dogs and cats, directly after extirpation of the laby- 
rinths lose their sense of orientation more or less, leads to the con- 
clusion that, in normal life, these animals use their labyrinths to 
obtain the orientation in space (in the air), and that for this purpose 
they use their eyes only when the labyrinths do not function properly. 
Within the first few days after bilateral extirpation of the laby- 
rinths it is easy to see how the animals gradually learn to use 
their eyes. 
