144 PROCEEDINGS OF SOCIETIES. 
edition, p. 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 en- 
larged 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, with accurate measurements of their angles and 
observations on the effects of polarized light, may, to speak 
medically, lead to an accurate diagnosis of them, as is afforded to 
the tests of the chemists, to whose larger operations they may be 
referred for further analysis. Dialysis affords us the means 
of separating the saline constituents of the juices of plants from 
the salts fixed in their tissues, and similarly in regard to animal 
bodies. By one or more dialytic operations on a limited scale 
the crystalloids of any vegetable juice may be obtained in solu- 
tion of great limpidity, and by careful evaporation over a water 
bath they will crystallize out in a state fit for examination.” 
Mr. Leigh concluded his paper by the quotation of some apposite 
remarks by the late Professor Johnstone, of Durham, and exhi- 
bited the small trays he uses in his experiments, consisting of a 
double rim of gutta percha securing a dise of parchment paper in 
the form of a sieve; also specimens of the mulberry-shaped 
nodules found in a steam-boiler, as before named. 
The Chairman said that for minute experiments he had used the 
parchment paper in the form ofa filter. 
Mr. Dancer stated that porous earthenware could be advantage- 
ously used as a dialyser. 
Professor Williamson indicated a number of subjects upon 
which dialysis would probably throw light, both in vegetable 
and animal physiology. He especially dwelt upon the pheno- 
mena of calcification and silicification, illustrating his remarks by 
reference to what occurs in the formation of calcareous and silicious 
growths in the colloid sarcode of sponges and polypifera, in the de- 
velopment of the dental plates of the teeth of Echinus, in the cal- 
cification of the derms of the crustacea, the shells of mollusca, the 
seales of fishes, andin the chondriform and membraniform bones 
and teeth of the vertebrate animals. The professor suggested that a 
natural process of dialysis probably underlay all these formations. 
He specially called attention to the close resemblance subsisting 
between the primary spherical and concentric granules seen 
in the derms of the crustacea, in the scales of cycloid and ctenoid 
fishes, in the outermost layers of many teeth, and the artificial 
concretions produced by Mr. Rainey, to which Mr. Leigh alluded 
in his paper. Professor Williamson further suggested for in- 
quiry, how far the structureless basement membrane seen under- 
lying the calcareous layer of many calcified structures (eg., the 
pulp-membrane of the tooth), played some part equivalent to the ~ 
parchment dialyser of the Master of the Mint. 
