36 WILLIAM PATTEN. 



last-mentioned organs. The flat triangular area on the ante- 

 rior margin of the under side of the cephalo-thorax is unusually 

 blunt to temperature changes. 



It is a remarkable fact that the regions so sensitive to 

 slight temperature changes can be touched with small wires 

 hot enough to singe the cuticula without producing any move- 

 ment. But if a rather large iron, about 2 or 3 mm. in diameter, 

 be held for a quarter of a minute on an abdominal appendage, 

 movements are produced, but they are evidently due to irrita- 

 tion of organs situated more deeply than those stimulated by 

 gentle breathing. 



A. Course of Temperature Impulses. — The following 

 experiments show the course of the temperature impulses to a 

 temperature centre, located somewhere in the fore-brain region. 

 Experiment^ A. — When a shallow longitudinal cut is made 

 on the ventral side through the skin along the lateral margin 

 of the right row of appendages, the temperature sense of the 

 carapace lateral to this cut is destroyed. On applying the 

 hand to the right side of the cephalo-thorax, either on its 

 dorsal or ventral surface, no movements are produced, but 

 when the same is done to the left side the legs on both 

 sides are set in motion. The roots of the great tegumen- 

 tary nerves (fig. 48, 2 — 6, a. m. p.) lie close to the ventral sur- 

 face along the outer margin of the legs, and as they are the 

 only ones severed by this proceeding, the experiment shows 

 that the temperature impulses travel centripetally 

 along the anterior and posterior hseraal nerves of the 

 thorax, not in all directions through the subdermal 

 plexus. It shows also that the temperature impulses 

 not only pass up and down the crura on the side 

 stimulated, but on to the opposite side as well. This 

 is in marked contrast with the gustatory impulses which give 

 rise to reflexes in those mandibles only that are stimulated. 



1 la my later experiments a ligature was drawn under the skin and tied 

 tightly around the nerve, thus obviating the disadvantage of excessive 

 bleeding. 



