1888.] Mr Irvine and Ur Woodhead on Lime Secretion, 315 
special development of carbonic acid gas, the phosphates of lime 
and magnesia predominate, calcium carbonate forming only about 
one-seventh of the bone salts. The osteoblasts are the secreting 
cells. It is scarcely necessary to point out that every gland and 
cell has its special form of secretion, and that it is quite as feasible 
that the lower part of the oviduct should secrete lime as that the 
upper part should secrete albumen, or the kidney water, urates, 
chorides, &c. As to the sulphur from the sulphate, it is probably 
partly used up in bile formation, and is partly excreted in the form 
of alkaline sulphides. 
Of course, all the above processes are merely suggested, but we 
shall take an early opportunity of acquiring more accurate data on 
the subject, as it is one that lies to hand. 
In the case of experiments on marine animals the matter is more 
difficult ; but by analogy some processes may be hinted at, and the 
conditions of conversion into, and secretion of, lime salts in the 
form of carbonates, may be assumed if we can obtain definite in- 
formation as to their secretion in the hen. That the process is the 
result of a combination of two forms of activity, — the purely 
chemical and what we must call vital, — must be taken for granted ; 
and it is this vital part of the process which aj)pears to eke out the 
possibilities of chemical reactions taking place. 
We think it is impossible, notwithstanding the means birds have 
at their disposal for reducing lime compounds to the finest state of 
division, that any lime can be carried mechanically, so to speak, 
from the gizzard to the oviduct ; indeed, our experiments seem to 
prove that such is not the case. Otherwise the shells of the eggs 
laid by the two hens during their confinement should have consisted 
of sulphate, and not of carbonate, of lime. 
There are many difficulties connected with an investigation such as 
that we have initiated, but chief among these is our ignorance of the 
changes effected by protoplasm upon the constitution of inorganic 
salts. We know that the decomposition of common salt in the 
process called digestion is the same as that which occurs when a 
solution of chloride of sodium is electrolysed. We also know that 
the chemical changes that occur in fermentation are due to the 
action of micro-organisms. It need not, therefore, be a matter for 
surprise that animals secreting calcareous matter should absorb 
