1888.] Dr A. B. Grififiths on tlu Malpighian Tubes. 
113 
of the tubes ; therefore the secretion contains sodium urate. This 
fact also points to the inference that sodium is a constituent of 
the blood of Tegenaria. 
Ko urea, guanin, or calcium phosphate could he detected in the 
secretion. This investigation proves the true renal function of the 
Malpighian tubes of the Araneina, 
2. The Hepatic Cells of Tegenaria domestica. 
The “ liver ” ducts (hepatic cells) are to he found anteriorly to 
the rectum (fig. la and b), and pour their secretions into the ali- 
Tig. 2 , — a and h. Crystals of Uric Acid and 
Murexide. a, the uric acid crystals 
covered with a brown pigment ; &, Murexide 
crystals. 
mentary canal (intestine). They appear under the microscope to 
consist of cellular tissue. The secretion of the “ liver ” of Tegenaria 
domestica^ when perfectly fresh, gives an acid reaction to litmus 
paper. The following reactions were obtained from the secretions 
of a very large number of animals : — 
1. The secretion forms an emulsion with oils yielding suhse- 
quently fatty acids and glycerol. 
2. The secretion decomposes stearin, with the formation of 
stearic acid and glycerol— 
C57HnoOr, + . 
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