GG8 Laura Florence 



numerous. Owing to the thickness of the cuticula it is impossible to 

 watch the pulsations of the heart in living specimens, as was done by 

 Landois (1864:11) and by Miiller (1915:29) in the clothes louse. 



The most successful preparations of the dorsal vessel have been obtained 

 by first removing the dorsal cuticula of the whole abdomen and then the 

 dorsal muscle plate. If the posterior attachment of the muscles of segment 

 9 be carefully loosened, the heart and its wing muscles will generally be 

 found intact on the ventral surface of the muscle plate. 



THE NERVOUS SYSTEM 



Since the time of Swammerdam (1682, English trans. 1758:36), it has 

 been known that lice possess three large thoracic ganglia and no abdominal 

 ganglia, and that nerves pass backward from the metathoracic ganglion 

 over the ventral stomach wall. It was not, however, until almost two 

 hundred years later that a more detailed description of the central nervous 

 system appeared, when Landois (1864:24) published his description of 

 Phthirius inguinalis. He referred to Swammerdam as correctly describing 

 three thoracic ganglia, and to Burmcister (1847) as incorrectly describing 

 two in the Pediculidae. He figured the brain, the connectives, and the 

 thoracic ganglia, but showed neither a sub-esophageal ganglion nor a 

 sympathetic system. In his study of Pcdiculus veslimenii, published a 

 year later (Landois, 1865 a : 54) , he found no noteworthj^ difference between 

 the species. Briihl (1871:477) devoted his attention chicflj^ to the study 

 of the peripheral ganglia, which he descril^ed as " Haar-Gehirne " and 

 of which he counted approximately one hundred and fifty on each louse. 

 Graber (1872:165) reviewed the work of Landois, and described the 

 connectives between the brain and the thoracic ganglia as being at least 

 four times the length given bj^ Landois. On one occasion he found and 

 figured a pear-shaped ganglion with two nerves passing backward from 

 it. Ho thought it was the hitherto undoscrilicd sub-esophageal ganglion, 

 but, since it lay on the dorsal surface of the esophagus, he concluded that 

 it must be a part of the visceral nervous system. JMjoberg (1910:222) 

 did no work on the nervous system, liut in a sliort note ho mentioned the 

 concentration of the ganglia in the thoracic region and the lack of any 

 detailed work in lioth Siphunculata (Anoplura) and Mallophaga. A 

 considerable advance has been made by ]\Iiiller (1915:32-37) in his 



