27 
found in the colon of a young man after death. 
about the size of a hen's egg, the others much smaller) were 
extracted from the rectum of a boy in the neighbourhood of 
Blackburn. By the liberality of Messrs. Coultate and 
Barlow, the whole are now deposited in the Museum of 
the Royal College of Surgeons. 
The concretions are of a light brown colour ; the ex- 
ternal coating is in parts firm and compact, and generally 
pretty smooth, and consists chiefly of a mixture of phos- 
phate of lime and ammoniaco-magnesian phosphate. In other 
places the surface has a velvety feel and is composed of very 
fine fibres closely matted or felted together, and in some 
places these fibres are collected into considerable masses, as 
may be particularly seen in the cross section of the remaining 
half of the one selected for chemical examination. The husk 
of an oat was imbedded in the surface of the calculus which 
had been sawed asunder before I received it. Their general 
structure is laminated, and consists of concentric alternating 
layers of the fibrous substance and the phosphates. The 
external form of the concretions is various ; three of them 
have assumed very solid figures, whilst the middle one of the 
three that were found lying together, is much flattened by 
the pressure of the outer ones. Their total weight, in the 
state in which I received them, was 22737 grains, or about 
4-| ounces. 
The largest weighed 1036 grains. 
The smallest - - 51 
They have all a very fetid disgusting smell. I found the 
specific gravity of the largest calculus at 6o°, to be 1.875. 
At first it floated in distilled water with nearly a fourth of 
its bulk above the surface, but after the air which filled its 
pores had been extricated, by placing it immersed in water 
