SPINAL REFLEXES. 833 



is eventually brought with unerring precision to meet the concurrently con- 

 tracted inbent portion of the nectocalyx. If one point of the nectocalyx be 

 irritated, and Avhile the manubrium is applied to that point, then another, 

 the manubrium will leave the first point and move over to the second. 

 In this way it may be made to indicate successively a number of points of 

 irritation. " After a series of such irritations, the manubrium subsequently 

 continues for some time to visit first one and then another of the points 

 which have been irritated." A cut between the base of the manubrium and 

 the point of irritation in the bell destroys the localisation, though move- 

 ment occurs toward some part of the quadrant of the bell containing the site 

 of stimulus ; but the accuracy of the localisation is reduced. The reaction 

 recalls the bending of the tentacles of Drosera i in the direction needful to 

 reach the seat of stimulation on the leaf. The headless bee stings in response 

 to stimulation of the under-surface pretty accurately at the site of irritation.- In 

 the " spinal " crayfish, if one leg is caught it is flexed and draAvn up, and soon all 

 the others, if the leg is not released, are brought round it and push at the 

 hand holding the limb. The yellow clover-fly has been observed, twelve hours 

 after decapitation, to stand cleaning its wings with its hind-legs, and to clean 

 its " three pairs of legs, rubbing them together in a determined manner, and 

 raising its fore-legs vainly in air as if searching for its head to brush up." 3 

 But in Astacus the accuracy of localisation is much impaired on the crossed 

 side by cutting the cross commissures combining the ganglia most closely 

 concerned with the reaction. 4 This recalls the effect of the tangential cut in 

 the nectocalyx of Tiaropsis. 



With the movement executed in a reflex reaction significant of " local 

 sign " in the above sense, the afferent impulses involved seem naturally 

 divisible into several groups according to their place of origin. There must be 

 (1) a group originated at the seat of stimulus, (2) a group initiated in the motor 

 and mobile organs reflexly set in action, and (3) in some cases a group originating 

 at a distant spot to which the movement is directed. Regarding this last group, 

 experiment illustrates its extinction, without extinction of the " local sign." 

 Thus, in Astacus, 5 after section of the nerve cords behind the mouth, when, 

 therefore, the hind creature without mouth has lost all nervous connection 

 with the front creature possessing the mouth, food given to the claws of the 

 hind creature is still at once and accurately carried by them to the mouth, 

 and this often refuses to take the morsel brought. In the grasshopper, after 

 extirpation of the supra- and suboesophageal ganglia (entire brain), the front leg 

 is protracted, 6 and in the normal way catches the antenna, and the usual 

 movements of cleaning the antenna go on, though the antenna has entirely 

 lost its innervation owing to the destruction of the brain. Regarding the 

 second mentioned group of afferent impulses, H. E. Hering has made an 

 interesting observation on the frog, and I have several times repeated it. 

 The " cleansing " reflex of the spinal frog which brings the foot to a seat of 

 irritation on the dorsal or perineal skin, is accurately executed after severance 

 of the afferent spinal roots of the limb itself. In the same way, the bulbo- 

 spinal frog brings the fore-limb to the snout when the snout is stimulated after 

 section of the afferent roots of the fore-limb. Guiding sensations for directing 

 the execution of these spinal cleansing reflexes are not essential ; the sole 

 important afferent factor as regards the local sign is restricted to the afferent 

 nerves of the place of initiation of the whole reflex. 



" Local sign," in the above sense, no doubt attaches to the motile 



1 Darwin, " Insectivorous Plants," London, 1875. 



'- Bethe, Arch./, d. ges. Physiol., Bonn, 1897, Bd. lxviii. 



3 A. H. Swinton, "Insect Variety," London, 1880 ; see also Grainger, op. cit. 



4 Bethe, Arch. f. d. gcs. Physiol., Bonu, 1897, Bd. lxviii. 



3 J. Ward, Journ. Physiol., Cambridge and London, 1879, vol. ii., and others. 

 6 Bethe, Arch. f. d. ges. Physiol., Bonn, 1897, Bd. lxviii. 



vol. ii.— 53 



