198 ANIMAL FORCES. [ii. 



a polype receives external impressions, they pass onwards (31) 

 to the nearest ganglion, whence they are reflected as if from a 

 brain, either entirely, or in such a way, that they only partly 

 reach other ganglia, and thus they can be reflected many times. 

 (Compare § 48.) It is sufficient that at these points the external 

 impressions are transformed into internal, and pass again from 

 the ganglia along the nerves to the mechanical machines, which 

 they put in motion, no act of thought taking place during the 

 transformation, because there is no brain (for in that only is 

 the seat of the conceptive force), nor are the internal impres- 

 sions adapted to excite a sentient action (97). In this way, 

 poises may be enabled to perform all their animal movements, 

 solely by means of external impressions on their nerves, without 

 having feeling, or thought, and without either brain or soul. 

 But inasmuch as all this is accomplished by means of animal 

 forces (32, 121), these animals do not act as mere machines, as 

 Descartes supposed, but according to purely animal laws, which 

 cannot be deduced from either mechanical or physical principles, 

 or explained by them. As Haller observes on the last page 

 of his introduction to the translation of Biiflijn^s ^^ History 

 of Nature,' they are animals whose life consists simply in 

 irritability. 



367. Other conclusions follow from the preceding propositions. 

 i. If the agency of material ideas on the cerebral origin of 

 the nerves, whereby they develop sentient actions in the me- 

 chanical machines, be sufficiently ascertained — that is to say, if 

 it be known on what nerve-fibrils, with what kind of stimulus 

 or movement, and in what direction and force, each received 

 material idea operates to produce certain sentient actions on 

 the muscles — another stimulus may be applied to the cerebral 

 origin of the nerves, or deeply in their trunks, instead of that 

 of conceptions, and thereby all the movements which the animal 

 performs as sentient acts, may be artificially produced without 

 brain, or mind, or conceptions, just as nature produces them in 

 anencephalous animals, by the transformation of the external 

 impression into the internal without any conceptions being 

 experienced. Thus, if the spinal cord or foot of a decapitated 

 frog be irritated, it moves from one place to another as if 

 acting volitionally, although deprived of both consciousness 

 and will (357, 359). 



