58 



consequence, the nerve responses are feeble, do not 

 perform autotomy very readily. 



2. The nerve of the limb must be sufficiently stimulated. 

 This appears to be a self-evident proposition. What- 

 ever may be the cause of autotomy, and whatever may be 

 the reason of this complex phenomenon, it is without 

 doubt the result of nervous stimulation. But the question 

 as to what is a " sufficient " stimulation cannot be disposed 

 of so easily (see below under the general discussion on 

 Autotomy). 



3. The thoracic nerve mass must remain intact. 



We are indebted to Fredericq* for his investigations 

 on the physiological processes involved in autotomy. He 

 has proved that the latter is the result of a reflex, and that 

 the thoracic ganglion belonging to the appendage is the 

 centre of this reflex. The brain is the seat of voluntary 

 and co-ordinated movement in Cancer, and if the brain be 

 removed autotomy will still take place. If, on the other 

 hand, the thoracic nerve mass be removed or destroyed, 

 self-amputation cannot proceed. The afferent nerve 

 fibres which are stimulated as the result of injury to the 

 limb are connected with the ganglion cells of the thoracic 

 nerve mass, and from these the efferent fibres pass to the 

 extensor muscle of the basi-ischium. This muscle is the 

 one 'Concerned in the autotomy, and thus we are provided 

 with a fourth condition. 



4. The integrity of the extensor muscle of the basi-ischium 



must bf, maintained. 



The first movement after the limb has been injured 

 is the extension of the basi-ischium; i.e., it moves in a 

 dorsal direction. This movement continues until the 



* Fredericq, L. " Nouvelles recherches sur 1'autotomie chez le 

 crabe." Archives de Biologic, T. XII, 1892. 



