Norman, Netvoiis System of Artktopods. 233 



ordination of motions (Burmeister, Lemoine and others), of 

 direction (Fauvre), or of a general center of motions 

 (Steiner). The animals experimented upon by me include the 

 most distantly related forms, — species in which in reference to 

 segmentation, and body-proportions the greatest differences 

 prevail. In all of these forms section of the oesophageal com- 

 missures (or removal of the brain, in which naturally the organs 

 innervated by the brain no longer came into consideration) was 

 in no case followed by paralysis in a single movable organ. 

 Likewise all of the more complicated reflex actions, which can 

 be observed in the normal animal (with the exception of such 

 as are to be regarded as having connection with both brain and 

 ventral cord) remain after isolation of the brain, as compensatory 

 movements of the eyes, walking and swimming movements, 

 flying movements, turning over when placed on the back, eat- 

 ing, copulation, cleaning legs and body, etc. [With Carcinus 

 the possibity of forward motion is lost. This is, however, a 

 special case, which will be more fully explained in a later paper]. 

 All motions are changed in so far as the tone of the muscles is 

 changed from that existing in the normal animals. I am of the 

 opinion that to this alone are due all the irregularities which ap- 

 pear in walking, swimming and flying. The essential point, it 

 seems to me, is that all the reflexes are still possible (auslosbar). 

 The changed tone which appears on removal of the brain, 

 is due to a general lowering of the muscular force, which may 

 be readily observed (especially if one of the commissures be 

 cut), in the case of Carcinus, Astacus, Squilla, and Dytiscus 

 by the difference in pressure exerted by the muscles of the two 

 sides against the hand of the observer. (In the case of Car- 

 cinus this difference was actually measured.) The changed 

 tone may also be observed in the stronger tension of 

 certain muscle groups over others, chiefly the flexors over the 

 extensors. This is shown by the position of the extremities, 

 which after the operation remain more strongly flexed than nor- 

 mally, especially in the coxal joints, thus causing the body to be 

 held higher than usual and in case of section of one of the oeso- 

 phageal commissures, or of removal of one half of the brain the 



