l86 FUNCTIONS OF THE BRAIN. 



region stimulated. The left legs make purposeful movements. The effect is not confined to 

 the appendage corresponding to the nerve stimulated, since after stimulating one nerve all the 

 legs of the opposite side are raised. 



b. Stimulation of the longitudinal integumentary nerve gave no results. 



c. The abdominal cord was transected between the neuromeres of the first and second gills. 

 Stimulating the proximal end of a haemal nerve in the isolated segment of the cord caused a 

 raising of the abdomen, followed by a very slight rhythmical movement of the gills. 



d. Stimulation of a branchial nerve causes a contraction of the legs and gills of the same 

 side, but no rhythmical movement. 



e. Stimulation of the right or left cord in front of the first abdominal ganglion causes con- 

 traction of legs and gills of the same side, but no rhythmical gill movements. 



PART II. 

 SUMMARY OF EXPERIMENTAL AND ANATOMICAL RESULTS. 



I. GUSTATORY REFLEXES. 



a. Normal Action. i. Each leg of the second to fifth pairs, when its taste organs are 

 stimulated, performs the chewing movements alone, without starting the action in the adjacent 

 legs of the same, or of the opposite side. 2. Stimulating the chilaria of one side may induce 

 chewing movements in all the legs of that side. 3. The chelicerse have no " taste spines." 

 They are brought into action by stimulating the taste organs on one or more of the other legs 

 of the same side. The action may then be transferred to its mate, if the stimulus is strong 

 enough. 4. When the taste organs of several legs on the same side are stimulated, all the legs 

 of that side work in a harmonious rhythm. 5. When both sides are stimulated, the rhythmic 

 movements of the right legs harmonize with that of the left. 6. There are two independent 

 movements in chewing, the lateral, or in and out movement of the jaw-like coxae, and the thrust- 

 ing of the tip of the legs in and out of the mouth. 



Structure of the Gustatory Apparatus. The principal reflexes described 

 above can be explained by the structure of the parts involved. The condi- 

 tions, so far as we have been able to analyze them by the anatomical and exper- 

 imental methods, are shown in a diagrammatic form in Fig. 114. We have 

 shown, for example, by the anatomical analysis, that : i. The taste organ nerves 

 of the jaws, flabellum, and chilaria form distinct fascicles, whose inner ends 

 (after giving off local dendrites, g.c. 1 ) unite to form an immense, longitudinal 

 tract, g.tr.y terminating in a voluminous mass of neuropile, or secondary taste 

 center, on the neuro-lateral surface of the cheliceral neuromere (diencephalon) 

 near the base of the cerebral peduncles, g.c. 2 2. A tract extends beyond this 

 center along the cerebral peduncles to a tertiary center that forms a large lobe on the 

 median face of each hemisphere, g.c. 3 At the base of the hemispheres, underneath 

 the posterior median lobes and on the anterior neural surface of the cheliceral 

 neuromere, is a group of large nerve cells, ch.Hc., which by one set of dendrites 

 bring the secondary taste center into relation with the cerebral cortex of the same 

 side, and by another set with the opposite side of the collar, through the forebrain 

 commissure. 4. Finally a cluster of about fifteen large nerve cells, H.as., 

 lying a little above the taste lobe, on the median surface of the hemispheres, 

 sends one set of extensive dendrites to the entire cerebral cortex, another to the 



