688 Ladea Florence 



epithelium, and appears to be continuous with the posterior end of the 

 chitinous bull) which marks the termination of the salivary duct. 



The two pairs of thoracic salivary glands lie closel}^ apposed to either 

 side of the anterior end of the stomach, and the long, horseshoe-shaped 

 gland is folded around the oblong-ovate gland in a characteristic manner 

 (Plate LXII, 3). In the man-infesting pediclili the glands are described 

 as " kidney-shaped " and " horseshoe-shaped," and their position in the 

 thorax has been variously figured by a number of authors but the smaller 

 one has never been shown surrounded by the larger. Strobelt (1882, 

 English trans. 1883:89) described the glands of Linognathus vituli (Haemato- 

 pmus tenuirostris) as " elongated " and " globular," and thought that 

 the efferent duct of the former was situated at one end of the gland and 

 that the horseshoe appearance was due entirely to the position of the 

 gland at rest. The length of the horseshoe-shaped gland (Plate LXII, 4) 

 is approximately 0.66 millimeter and the width of the arms 0.33 miUi- 

 meter. The length of the oblong-ovate gland (Plate LXII, 5) is 0.12 mil- 

 limeter and its width 0.05 millimeter. The large cells of the epithelial 

 lining shine through the outer membrane of the gland, and at the exit 

 of the duct the transition from these to the small cells lining the duct can 

 be seen even in gross specimens (Plate LXII, 6). In sections the epithelial 

 cells are seen to be considerably larger than those of Pawlowsky's glands, 

 and the nucleus, with its dark-staining nucleolus, lies rather toward the 

 base of the cell. There is a distinct though small kmien within each 

 gland. The efferent ducts of the two glands pass cephalad without 

 uniting. In gross dissection they have been followed as far as their 

 entrance to the head, but their union with the salivary duct lying between 

 the dorsal and ventral elements of the piercers has not been seen. In 

 his description of dissections prepared by Mr. Bacot, Entomologist to 

 the Lister Institute, and the late Major Sidney Rowland, of the Royal 

 Army Medical Corps, Martin (1913:85) says the four salivary ducts 

 open into the base of the piercer sheath; while Harrison (1916b: 209) has 

 not succeeded in tracing definite connections between the salivarj^ duct of 

 the mouth parts and the ducts of the glands. Sikora (1916:56) describes 

 the ducts as passing into the head alongside the esofihagus as far as the 

 posterior end of the sub-esophageal ganglion, where thej' turn back, 

 and through a ventro-caudal bend reach the end of the piercer sheath. 

 In Pediculus vestimenU she figures the two ducts of each side as uniting 



