53 
natans covered with Membranifera ; and Cresia aciculuta, a 
Pteropod. 
Mr. John Hep worth referred to the mildew mentioned 
in the proceedings of the previous meeting, .which had been 
observed at Gibraltar on fustians stiffened with bone size, 
and stated that he had noticed a peculiar fungoid growth 
upon mounted sections of bone, and that it would be desirable 
if possible to compare them. 
Mr. John Leigh, M.R.C.S., read a Paper On the Use 
of Dialysis in Microscopical Investigations.” 
After describing the researches of Professor Graham, the 
present Master of the Mint, and explaining the nature of the 
division into two classes of all natural bodies, namely, into 
crystalloids and colloids, their affinities and means of separa- 
tion, the Author proceeded to describe some curious bodies 
found in cleaning out a steam boiler, which have almost 
exactly the external form and internal structure of the con- 
cretions formed by Mr. Rainey, and figured in Dr. Carpenter’s 
work on the Microscope, third edition, page 769. They are 
composed chiefly of carbonate of lime and organic matter 
aggregated in the presence of the aluminous colloidal mud 
in the boiler, and are, on a large scale, a singular illustration 
of Mr. Rainey’s experiments. The Author then enlarged 
upon the advantages of this method of investigation to the 
microscopist and chemist, who may go hand in hand in the 
examination of the crystalloidal constituents of organic 
bodies. “ The microscopist (says the Author) will often be 
able to direct his fellow worker into new channels of research. 
A careful study of minute crystals, ivith accurate measure- 
ments of their angles and observations on the effects of 
polarised light, may, to speak medically, lead to an accurate 
diagnosis of them, as is afforded to the tests of the chemist, 
to whose larger operations they may be referred for further 
