30 C. WINKLER. THE CENTRAL COURSE 



the operation, have been turned round in such a manner that for 

 a normal animal it becomes impossible to remain seated on the 

 ground with its lower extremities, its forepart having assumed a 

 forced attitude, exceeding a certain degree. All the more so , because 

 of the fact that this position does not retain permanently the same 

 intensity , but is at intervals suddenly intensified. 



If the rabbit, like the pigeon, did possess a long and easily 

 movable neck, that could be laid down on the ground and find 

 a support there, whilst the head was being turned upward, then 

 the turning might perhaps, as it is in pigeons, still be checked, 

 and the turning of the head only, might occur until 270 or even 360. 



Now this is impossible in rabbits. Therefore the animals roll. This 

 rolling of the body round its longitudinal axis is therefore always 

 accomplished in two tempo's. The first automatic tempo of the 

 rolling is the same as it is observed in pigeons. The head is thrown 

 vigorously towards the operated side, and turned so far, that its 

 dorsal cranial plane touches the ground. The head then turns 180. 

 As is described already, at this moment the upper extremity 

 of the opposite side, drawn by the movement of head and neck, 

 is extended and abduced as far as possible from the body, and 

 by scratching the ground tries to prevent a further turning of the 

 head. But if once the head has been turned further, if its dorsal 

 plane touches the ground, if the turning surpasses 180, the aid 

 of the upper extremity becomes useless. The extremity is itself turned 

 upward, and at the moment when it does arrive in the vertical 

 plane, (the turning of the head then reaches 270) the second 

 tempo of the rolling sets in with a vigorous jerk, and the hind 

 part of the body is thrown round by the animal by an energetic 

 voluntary movement. The fact, that the rolling of the body round 

 its longitudinal axis is always preceded by a very intense turning 

 of head and neck, supports the probability that the mechanism of 

 the revolution may be a consequence of the automatic initial tur- 

 ning of neck and head. 



After a few days however the rolling ceases. Then follows a 

 period after the operation, wherein the rolling may be at any 

 moment provoked .again by laying down the animal on its non- 

 operated side. The head is then jerked violently towards the 

 operated side and .the revolution follows. After a week perhaps 

 this also ceases. It may still occur sporadically in the second week 

 after the operation , but after three or four weeks the animal does 

 no longer roll round its axis. Head and neck still are turned , but 

 this characteristic position has no longer the same intensity it 



