1888.] Mr Irvine and Dr Woodhead on Lime Secretion. 313 
presence of putrefying organic matter, it is quite possible that there 
is a formation of the sulphide of calcium and then of the phosphate 
or chloride of calcium. 
The gases present in the alimentary canal are not derived merely 
from the decomposition of undigested food, but are thrown out in 
great part by the various secreting surfaces. In the stomach the 
gases consist principally of those derived from the air ; in the small 
intestine, as Pasteur has pointed out, the quantity of carbonic acid 
gas rises, that of nitrogen falls, and hydrogen is developed. In the 
large intestine the carbonic acid gas still increases, the other two 
gases are diminished in quantity, and sulphuretted hydrogen is 
developed in small quantities. 
In his experiments on putrefaction, Pasteur has shown that, as 
starch and sugar are converted into lactic and butyric acids in 
the presence of micro-organisms, there is an evolution of carbonic 
acid gas and hydrogen. He further points out that, when oxygen is 
absent, reductions take place, oxyacids are reduced to fatty acids, 
and hydrogen, carburetted hydrogen, and sulphuretted hydrogen are 
formed. It is therefore evident that the sulphate of lime may be 
converted, in the intestine, into a sulphide, and thence to a chloride 
or phosphate. Further, in the processes above referred to, fatty 
acids are formed which would decompose the sulphide of calcium, 
forming lime soaps and setting free sulphuretted hydrogen. How 
comes a curious fact : if lime soaps be mixed with cloacal mucus 
calcium carbonate, carbonic acid gas, and hydrogen or carburetted 
hydrogen are formed (Landois and Stirling’s Physiology, 2nd ed., 
vol. i. p. 401), the calcium formiate yielding calcium carbonate, 
carbonic acid gas, and hydrogen ; calcium acetate, under the same 
conditions, producing calcium carbonate, carbonic acid gas, and 
carburetted hydrogen as a result of the putrefactive fermentation. 
In the food taken by fowls there is usually a considerable 
quantity of phosphorus, a large proportion of which combining 
with the reduced sulphate of lime would account for the presence 
of the phosphate of lime in the excreta. Beyond this, however, it 
is possible that the lime may be carried to the secreting surface of 
the duct as a soluble phosphate of lime and soda, as calcium 
chloride, and as lime soaps (in combination with the fatty acids), or 
even as the carbonate. 
