112 Proceedings of Boyal Society of Edinhurgh. [jan. 6, 
ethyl alcohol and filtered. Boiling water was poured upon the resi- 
due, and an excess of pure acetic acid added to the aqueous filtrate. 
Intestinel 
Rectum 
Fig. 1 . — Tegenaria domestica. A dissection showing the position of the 
Malpighian tubes and the so-called “liver.” A (greatly enlarged) ; 
B shows the same parts, hut isolated from the abdomen. 
After standing eight hours, crystals of uric acid made their 
appearance, and were easily recognised by the chemico-microscopical 
tests already mentioned. 
The waste nitrogenous products of Tegenaria domestica are con- 
verted by the Malpighian tubes into uric acid ; but the uric acid is 
not in that condition (^.e., the acid condition), for it was found in 
combination with sodium. Sodium is easily found in the secretions 
