54 
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 solution 
of great limpidity, and by careful evaporation over a water 
bath they will crystallise 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 exhibited the small trays he uses in his experiments, 
consisting of a double rim of gutta percha securing a disc 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 of a filter. 
Mr. Dancer stated that porous earthenware could be 
advantageously used as a dialyser. 
Professor Williamson indicated a number of subjects upon 
which dialysis would probably throw light, both in vegetable 
and animal physiology. lie especially dwelt upon the 
phenomena of calcification and silification, illustrating his 
remarks by reference to what occurs in the formation of cal- 
careous and silicious growths in the colloid sarcode of sponges 
and polypifera, in the development of the dental plates of 
the teeth of Echinus, in the calcification of the derms of 
the Crustacea, the shells of mollusca, the scales of fishes, 
and in the chondriform and membraniform bones and teeth 
of the vertebrate animals. The Professor suggested that a 
natural process of dialysis probably underlay all these forma- 
tions. 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, 
