The nervous system in the Cestode Moniezia expansa. 373 



Luhe and Cohn, as accompanyiuf^ each of the lateral nerve trunks. 

 P'or the first 5 mm behind the scolex the lateral nerves are of uni- 

 form diameter, they possess only a few ganglionic cells and no trace 

 of ganglionic enlargements. The "binding" cells enveloping them are 

 few, long tracts existing without any such elements. The branches 

 arising from the lateral nerves are mostly limited to the formation of 

 the dorsal and ventral commissures (PI. 21, Fig. 1). 



The dorsal and ventral nerves are likewise without ganglionic 

 enlargements in the neck region, and the ganglionic cells are few. In 

 the posterior part of the neck region where the proglottides begin to 

 be distinguishable, the nerves begin to assume the condition which 

 they present in the mature segments. In this portion of the neck 

 region each lateral nerve begins to exhibit an enlargement at a point 

 near the posterior margin of the proglottis. This enlargement is due 

 to the increased number of ganglionic cells occurring in the nerve at 

 that point; these increase in number continuously until the proglottis 

 is mature. The enlargement of the lateral nerve caused by this in- 

 crease in the number and size of the ganglionic cells is the first in- 

 dication of the posterior lateral ganglion (PI, 21, Fig. 1 gnd.p). The 

 position of these ganglia is indicated in the preceding portion of the 

 neck region by the presence of the small branches from the lateral 

 nerve which correspond in position to the posterior part of each young 

 proglottis. These branches are undoubtedly the beginnings of the 

 dorsal and ventral commissures of the mature segments which are 

 recognizable, then, before the ganglionic enlargements of the lateral 

 nerve with which they are connected. 



At a distance of 30 mm from the scolex the posterior lateral 

 ganglia are well marked. In favorable sections from this region made 

 in a frontal plane it is possible to trace the individual neurons of 

 the lateral nerves (PI. 26, Fig. 32). The ganglionic cells are usually 

 nearly triangular and of the unipolar type ; there are a great number 

 of dendritic, or protoplasmic, processes which interlace with those of 

 neighboring ganglionic cells. In the section shown in PI. 26, Fig. 32, 

 there are three unipolar and two bipolar ganglionic cells, which, for 

 some reason, are more deeply stained than the others. At least two 

 kinds of neurons are distinguishable ; in one the ganglionic cell sends 

 a nerve fibre posteriorly from its ganglion to the next following one; 

 in the other anteriorly to the preceding ganglion. A complete iso- 

 lated neuron is shown in PI. 24, Fig. 25. 



In each of the ganglionic enlargements there lie between the 



