440 HYDE. [Vor Ix. 
(c) When Limulus masticates and swallows food, respiratory 
activity that has been temporarily stopped will immediately be 
aroused. This is true, not only in a decapitated Limulus, but 
also in one that had the entire brain, post-oesophageal ganglion, 
and all but three ganglia of the collar extirpated. 
If food is swallowed by a Limulus whose gill-plates were 
divided into two divisions by lesion, both divisions increase in 
rate. If the anterior is moving normally and the posterior is 
motionless, the anterior moves with greater extent, and the 
posterior immediately begins respiratory activity. 
The above facts show that it is not cerebral activity that 
influences respiration at the time of feeding. It may be the 
gastric and intestinal movements that reflectorally affect the 
respiratory mechanism. 
When a Limulus is in a dying condition its respiratory 
activity is greatly altered. In one Limulus that had the cord 
cut anterior to the operculum (O Fig. 1) the respiration was 
characterized by intervals of rapid and exaggerated inspira- 
tions that gradually lessened and were then followed by periods 
of cramp movements. In another striking case the respiration 
of the last day was marked by movements that ultimately 
declined to complete cessation and returned to an amplitude 
much above the normal; resembling, to a certain extent, the 
Cheyne-Stokes respiration of higher animals. 
B. Reflex Actions. 
(z) If we apply external stimuli to a normal Limulus, its 
respiratory movements can be altered, and it behaves in a 
peculiar manner. 
When it is placed on its back, and its spine, appendages, 
gill-plates, or any part of the ventral carapace is pressed with 
fingers or forceps, the gill-plates stop in the expiratory 
phase about as long as the pressure lasts (several minutes), 
at the same time the animal usually turns onto its ventral 
side ; or it turns its abnormal carapace ventrally, the spine 
forward and pulls the appendages into the cavity of the 
cephalo-thorax. 
