G70 Laura Florence 



ganglia. They measure approximately 0.22 millimeter in length. The 

 thoracic ganglia are large and broad. Their approximate length is 0.38 

 millimeter and width 0.28 millimeter. They are closely fused, showing 

 neither connectives nor commissures, but both in gross specimens and 

 in sections it is evident that each ganglion has arisen through lateral 

 fusion of two ganglia. They lie in the most anterior part of the thorax, 

 and when the stomach is distended their position is oblique dorso-ventral 

 rather than ventral. All three send out lateral nerves to the legs and the 

 thorax, and the metathoracic ganglion sends in addition eight nerves 

 to the alDclomen, of which the tv/o nearest the median line are the largest. 

 These nerves pass backward to the ninth abdominal segment and give 

 off in their course many slender branches to the visceral and reproductive 

 organs. 



The sympathetic system is well developed. The frontal ganglion is 

 somewhat pear-shaped and lies some 0.03 millimeter in front of the brain, 

 on the median line above the junction of the pumping phar3'nx with the 

 true pharynx. Slightly laterad on either side of the ganglion a small 

 nerve is given off anteriorly from the branches connecting the ganglion 

 with the brain. The course of these nerves has not been seen, but they 

 may connect the frontal ganglion with two smaller ganglia which are 

 united to each other and lie on the median line above the anterior part of 

 the buccal plate of Harrison (Plate LX, 1). Similar ganglia have been 

 seen by Sikora (1916:28) in the clothes louse, and she has suggested that 

 they are homologucs of the prefrontal nerve plexus described in other 

 insects. From the anterior end of the frontal ganglion a nerve passes 

 forward on the metlian line, and from it numerous lateral branches are 

 given off. From the posterior end of the frontal ganglion the recurrent 

 nerve runs back, passing under the brain close to the dorsal surface of the 

 esophagus and finally terminating in the thorax in a small ganglion 

 situated above the entrance of the esophagus into the stomach. From 

 this ganglion at least two slender nerves pass backward over the dorsal 

 stomach wall. 



Both in gross dissections and in the study of serial sections, two sub- 

 circular structures, of a diameter approximating 0.03 millimeter, have 

 been found under the protocerebral lobes of the brain. They are made 

 up entirely of ganglion cells, show no central substance, and stain more 

 deeply than the surrounding tissues. In no case has any coimection 



