1888 .] Dr A. B. Griffiths on the Malpighian Tubes. 
Ill 
6. Investigations on the Malpighian Tubes and the 
“ Hepatic Cells ” of the Araneina ; and also on the 
Diverticula of the Asteridea. By Dr A. B. Griffiths, 
F.R.S. (Edin.), F.C S. (Bond. & Paris), Princi]pal and Lec- 
turer on Chemistry arid Biology^ School of Science^ Lincoln; and 
Alexander Johnstone, F.G.S. (Bond. & Edin.), Assistant 
Professor of Geology and Mineralogy^ University of Edin- 
burgh., <^'C. 
The present memoir is a continuation of those already published 
by one of us, on the physiology of the Invertehrata. 
1. Malpighian Tubes o/Tegenaria domestica. 
The intestines of Tegenaria domestica form a tuhe-like body, 
which dilates into a short rectum, and into this rectum the Mal- 
pighian tubes open (fig. 1, A and B). The secretion obtained from 
a large number of these tubes yields uric acid. The secretion is 
neutral to test papers. 
The secretion was examined chemically by two separate methods : 
— (a) The clear liquid from the Malpighian tubes was treated with 
a hot dilute solution of sodium hydrate. On the addition of hydro- 
chloric acid a slight flaky precipitate was obtained after standing 
six hours. These flakes were seen (under the microscope) to con- 
sist of rhombic plates (figs, ^a) and other crystalline forms. When 
these crystals are treated with nitric acid and then gently heated 
with ammonia, the beautiful four-sided prisms of reddish purple 
murexide [CgH 4 (N’H 4 )N' 50 g] are obtained (fig. 25). The crystals 
(another portion) produced by sodium hydrate solution were dis- 
solved in a drop or two of sodium carbonate solution, and then 
poured upon a piece of filter paper moistened with a solution of 
silver nitrate, when a dark brown stain of metallic silver was pro- 
duced : thus showing, according to the test of Schiff, the presence of 
uric acid. 
ib) Another method used was as follows (for testing the secretion 
of the Malpighian tubes of Tegenaria) : — 
The secretion was boiled in distilled water, and evaporated care- 
fully to dryness. The residue obtained was treated with absolute 
