336 Proceedings of Royal Society of Edinburgh. [sess. 
carbonic acid. How marked are the differences in the proportions 
in Herbivora and Carnivora may be gathered from the analyses 
collected by Liebig (Letters on Chemistry , p. 406), from which we 
gather that the ash of human blood contains 32 per cent., that of 
the pig and the dog 36 per cent., that of the fowl 40 per cent., 
that of oxen and sheep not more than from 14 to 16 per cent, 
of phosphoric acid, though calves’ blood contains about 20 per cent. 
The carbonic acid varies inversely. In the ash of human blood we 
have only 3*78 per cent., in that of ox blood 18 ’8 5 per cent., in 
that of sheeps’ blood 19*47 per cent. In these cases, where the 
proportion is large, however, the carbonate of lime is secreted by 
the kidney cells, and is carried off in solution in the urine instead 
of being secreted • as a shell. In whatever proportions the acids 
are present they are always neutralised by a slight excess of the 
alkalies and alkaline earths. 
Schmidt* found that the blood of the pond mussel (Anodonta 
cygned) was slightly alkaline. He describes as present on evapora- 
tion beautiful crystals of carbonate of lime resembling gaylussite. 
These could not have been present originally in the alkaline fluid, 
and it is probable that they were produced by the formation of 
carbonate of ammonia from the decomposition of urea and nitro- 
genous organic matter. 
This must occur in the case of the effete matter discharged by 
animals. The carbonate of ammonia produced by the decomposition 
of urea, &c., decomposing a portion of the sulphate of lime in the 
sea water with the formation of carbonate of lime equivalent in 
amount to the carbonate of ammonia thus formed. 
According to Lehmann,! carbonate of lime in considerable quantity 
is found in the urine of graminivorous animals, in the saliva of the 
horse, and in many animal concretions. The urine of graminivorous 
animals often contains so large a quantity of carbonate of lime as to 
cause a deposit very soon after its emission. “ My investigations 
tend to show that in the urine of the horse * carbonate of potash 
and carbonate of lime very frequently replace one another ; I have 
usually found the urine rendered turbid by the presence of much 
carbonate of lime, which contains a very small quantity of alkaline 
* See Taylor’s Scientific Memoirs , vol. v. p. 26. 
t Loc. cit. } vol. i, p. 419 (see also references on p 2'40). 
