HUMAN GALL STONE. 
247 
ART. LII.— ON THE SOURCE, PHYSICAL AND CHEMICAL 
PROPERTIES, OF A SPECIES OF HUMAN GALL STONE. 
By E. Neal, M. D. 
These biliary concretions are often found in the hepatic 
and cystic ducts, or in the common duct of the liver, but by 
far the greater number, are derived from the gall-bladder 
itself, in which they are usually formed. At a post-mor- 
tem examination of a man, aged 80 years, we removed from 
that viscus, fourteen calculi which present the following 
characteristics. 
They have a smooth surface , a tetrahedron form, with 
the angles somewhat rounded ; are of a size varying from 
that of a pea, to a grain of Indian maize, having like it a 
fine yellow color, striated with lines of a dark brown. 
This coloring matter forms a crust of about two lines in 
thickness, is of a short fracture, easily broken off, enclosing 
a dark brown nucleus. They are insipid, and inodorous, 
having a greasy feel when rubbed between the fingers, 
and a specific gravity, little inferior to that of water, being 
about 0.99S. 
They are insoluble in water, and, when whole, in cold 
and boiling alcohol of 35° Baume ; in the volatile oils and 
spirits of turpentine, in the dilute and strong acids, although 
the nitric changes their yellow color to a light red : but 
when powdered they are nearly soluble in boiling alcohol 
and ether. In a dilute solution of pure potassa, they 
undergo no change at the ordinary temperature, but in a 
strong solution, at the boiling point, they- are partially solu- 
ble, the color changing during solution from a yellow to a 
blue, which is soon altered by contact with atmospheric air 
to a fine emerald green; which, again, by successive addi- 
tions of nitric acid, is converted to a blue, violet and red, in 
the course of a few seconds. They melt at the temperature 
