184 
ON THE NEPHROCYTES OF PEDICULUS HUM ANUS. 
By GEORGE H. F. NUTTALL, F.R.S., 
and D. KEILIN, Sc.D., 
Beit Memorial Research Fellow. 
{From the Quick Laboratory, University of Cambridge.) 
(With 5 Text-figures.) 
CONTENTS. 
PAGE 
Introduction . . . . . . . . 184 
Peri-oesophageal nephrocytes in Pediculus . . . 185 
Disseminated nephrocytes in Pediculus . . . . 186 
The physiological function of nephrocytes . . . 187 
Method of intra-coelomic injection in Pediculus . . 188 
Results of intra-coelomic injections in Pediculus . . 189 
Nephrocytes of Mallophaga ...... 191 
Nephrocytes of Pediculus and Diptera compared . . 191 
Summary ......... 192 
References . ....... 192 
Introduction. 
Dissections of the thorax of Pediculus humanus <$, $, or larva, demonstrate 
the existence of two groups of special cells lying suspended on either side of 
the oesophagus between the reniform salivary glands and the forwardly pro¬ 
truding intestinal caeca. These cells have already been observed by ento¬ 
mologists who have studied the anatomy of the louse; Patton and Cragg 
(1913, p. 559, PI. LXX, figs. 1 and 2) were the first to see and figure them. 
These authors refer to them as follows: 
“Embedded among the fat body, immediately anterior to the kidney¬ 
shaped glands, there is on each side a small collection of round cells, readily 
distinguished from the fat body by their more glistening appearance. These 
are constant in position, and are always found, in sections and dissections, 
surrounding the oesophagus, though not attached to it in any way. They 
have no capsule, but appear to be connected with one-another by short and 
pointed processes. The protoplasm of these cells is vacuolated, and contains 
many fine granules. One, or sometimes two, nuclei are present, and appear 
as clear vesicles containing a darkly staining mass of chromatin. No duct 
has been distinguished with certainty, though in some dissections a fine 
