1888 - 89 .] Mr Irvine & Dr Woodhead on Carbonate of Lime. 349 
acid, but in this case the precipitate formed is found to be 
carbonate of lime, the precipitation in both cases being facilitated 
if the clear solutions are maintained at a temperature of 90° F. 
When a mixture of alkaline phosphates and carbonates and soluble 
lime salts are so treated, the precipitate which results is found to be 
a mixture of phosphate and carbonate of lime — the amounts varying 
with the proportion of the salts present. 
Thus bone contains from 50 to 60 per cent, phosphate, and from 
6 to 10 per cent, carbonate of lime, and the calcareous shells of 
crustaceans and eggs of birds contain from 60 per cent, to 80 per 
cent, carbonate with 1 to 2 per cent, phosphate of lime. 
We have thus given a rational explanation of the chemical changes 
which probably govern the secretion of different lime salts by animals, 
but in such investigations, dealing with matter in its relations to 
protoplasmic or vital force, we can only reason by the inferences we 
may draw from the imperfect knowledge we obtain experimentally 
in the laboratory. 
The ordinary methods of analysis fail to give us an accurate 
knowledge of the relative position occupied by matter in the 
complex relations existing in such conditions. 
Summary. 
We assume that the greater part of the carbonate of lime in the 
ocean-beds is the result of animal life. 
Soluble carbonate of lime is present in very small quantities in 
sea Water, but other salts of lime, especially the sulphate, are 
present in larger quantities. 
Hens supplied with sulphate of lime, but no other lime salt, 
produce well-formed egg-shells composed of carbonate of lime. 
In the organs of the body, gizzard crop, and faeces of a hen so fed, 
only a small quantity, 10‘08 grs. of carbonate of lime was found, 
but there was a considerable quantity of phosphate of lime present. 
(It was afterwards found that sufficient carbonate of lime, for the 
formation of the shells of two, eggs, could be stored up in the crop, 
gizzard, &c.). 
In the alimentary canal sulphide of calcium and then phosphate 
or chloride of calcium, or lime soaps may be formed. These latter, 
