692 Laura Florence 



since the longitudinal fibers are gathered in six strands. There is no valve 

 between the stomach and the small intestine. 



Between the small and large intestines is a region, measuring 0.25 

 millimeter in diameter, which is characterized by the presence of six 

 whitish, oblong-ovate plates imbedded in its wall (Plate LXII, 7). These 

 plates, which in sections (Plate LXII, 8) are seen to extend a considerable 

 distance into the lumen of the intestine, are surrounded by a large number 

 of tracheae. They have no definite cell structure, their content is 

 granular with nuclei scattered throughout, and in some sections irregular 

 clefts are present which are evidently not due to mechanical rupture 

 and may be definite lumina. No ducts opening into the intestine have 

 been seen. With hematoxylin and eosin the groundwork stains an uneven 

 pink, and with iron hematoxylin a light grayish brown. Whether these 

 plates are modified glands is uncertain. Their inner surface is lined with 

 a well-defined intima, and at either end a definite epithelium is represented 

 by a few cells in the clefts between the plates, but in the middle of the 

 region (Plate LXII, 8) no such cells are to be found. The inner layer of 

 circular muscle is present, and the longitudinal muscle consists of six 

 bands each made up of six or seven fibers lying in the indentations between 

 the plates, but no outer circular layer has been seen. Sikora (1916:67-68) 

 calls these plates the " Enddarmdriise," and objects to the use of the 

 name " rectal glands " on the ground that in the louse these plates have 

 no connection with the rectum. Her figures of their structure in Pediculus 

 vestimenti represent them as much more glandlike than they appear to 

 be in Haernatopinus suis. Toward the posterior end the cuticula increases 

 considerably in thickness and the plates are succeeded by a well-defined 

 epithelium. The longitudinal muscle fibers are lost sight of among the 

 large circular fibers surrounchng the rectum (Plate XLII, 9). This is a 

 short, straight tube leading direct to the anal opening and measuring 

 only 0.18 millimeter in length and, 0.08 millimeter in diameter. Its wall 

 lies in six folds, and it is lined by a thick cuticula which is not verj' strongly 

 chitinized and stains a clear blue with Mallory's connective-tissue stain ' 

 after fixation in picro-aceto-formol. 



FEEDING AND DIGESTION 



In experimental feeding, when a louse is placed on the arm it crawls 

 around and appears to test the surface with the antennae and the sensitive 



