THE NERVOUS MECHANISM 
OF THE. RESPIRATORY MOVEMENTS. “IN 
LIMULUS POLYPHEMUS. 
MISS IDA H. HYDE. 
Tue following paper gives the results of experiments on the 
nervous mechanism of the respiratory movements in Limulus, 
which were made under the instruction of Dr. Jacques Loeb 
during the summer of 1892 in the Marine Biological Laboratory 
at Woods Holl. 
Very few investigators have experimented to determine the 
influence of the nervous system on the respiration of inverte- 
brates. Of these, Faivre’s work on Dytiscus (iv) is the most 
important. He found that in Dytiscus the respiratory mech- 
anism is controlled by three centres: (2) the metathoracic 
ganglion, which presides over respiration, (4) the suboesopha- 
geal ganglion, which coordinates respiratory with post-abdom- 
inal movements during walking or swimming, and (c) the 
abdominal ganglionic cord, serving as a conducting organ for 
the centres. 
Limulus is in every respect a more favorable subject to 
experiment on than is Dytiscus or any other invertebrate that 
I know of. Its power of endurance is unequaled, and its large 
size enables one to operate on it with great certainty and ease. 
The object of the experiments was to determine by which 
region of the nervous system and in what way the mechanism 
of respiration was controlled. 
The abdominal ganglionic cord in Limulus (D Fig. 1), as 
we shall see, is the only part of the nervous system concerned 
in the respiratory movements. Therefore, it alone requires 
description. The double nerve cord is inclosed in an artery 
and extends along the ventral side of the abdominal region to 
the arms. It contains six ganglia, from each of which arise 
two pairs of nerves. The first five larger or posterior pairs of 
