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upon guinea-pigs, the reactions found in these animals may be shortly 
recorded here. 
Lift reactions. 
The animal sits in a normal posture upon a plank held horizontally. If the 
plank be moved vertically upwards, it will be seen that at the commencement 
of the movement the fore-legs are bent sharply and the head droops. 
When the movement of the plank ceases, the fore-legs will be stretched 
straight out, the fore part of the body is lifted, and frequently too the head 
is bent backwards. In strong reactions the hind-legs act too, till finally the 
animal stands upon its four extended legs. The reverse reaction takes place 
when the movement is downwards. When the movement commences, the 
extremities, and especially the fore-legs, are extended, and the front part of 
the body raised. On the cessation of the movement, the fore-legs are bent 
and the head and front part of the body droop towards the plank. 
Muscular vibrations. 
The animal is held vertically in the air with the head upwards, the thumb 
and little finger of the left hand lie round the belly, the fore and third fingers 
support the fore-legs, with the hind-legs resting upon the palm of the hand, 
while the thumb and forefinger of the right hand rest upon the neck and 
shoulders of the animal. The head is in the normal position. One must wait 
until the animal is perfectly quiet and the fingers of the right hand no longer 
feel any muscular vibrations in the shoulder and neck muscles. Then, if the 
animal be moved vertically (up and down), or horizontally (ventrally, dorsally, 
to right and left), the right hand during these progressive movements will feel 
a distinct muscular vibration. Closer attention will reveal that here, too, the 
“vibration takes place at the commencement and end of the movement. 
The spreading of the toes. 
The guinea-pig is held vertically in the air, the right hand under the arm- 
pits with the palm of the hand turned towards the back of the animal. The 
toes of the hind feet are. then carefully stroked together. If the animal be 
then moved even very slightly downwards, the toes of the hind feet will 
immediately spread apart. 
The reaction can be demonstrated with most, though not with all animals, 
and occurs at the beginning of the movement. If the animal be moved in 
the same way upwards, the toes will also be spread, this occurring some 
times at the commencement and sometimes at the close of the movement. 
All these reactions upon progressive movements are dependent upon the 
labyrinths, and are not visible after a double labyrinth extirpation. We cannot 
enter here into details, neither can we discuss the precautions to be observed 
in the investigation. These will be given in more detail later, when also 
some other labyrinthic reactions upon progressive movements will be described. 
As was mentioned above, Macu and Brever believed on theoretical 
considerations that it was physically impossible that the semi-circular - 
canals had anything to do with these reactions, and therefore came 
to the conclusion that only the otolithes were accountable for these 
