428 DISEASE IN WILD MAMMALS AND BIRDS 
protein catabolism, and through the overstimulation of 
the digestive tract, may interfere with the absorption 
of food. 
Sulphur is largely taken into the body in organic 
combination mth the protein, (a very little inorganic 
sulphur appears in the drinking water) therefore if the 
protein requirements are adequate the sulphur will 
usually be adequate. 
Magnesium is abundant in meat and most plant 
tissues ; so that except in diets of highly refined foods, it 
is more often excessive than deficient. 
The other elements, calcium, phosphorus and iron are 
frequently insufficient, especially for animals on omniv- 
orous diet (cf. Table 20). Phosphorus enters into 
every living cell, and in cases of starvation is excreted 
up to the last. It is involved in practically all the cell 
functions. In the body it is present (1) as an inorganic 
compound in the bone tissues and blood where it helps to 
maintain neutrality, (2) as phosphorus-containing pro- 
tein, phosphatids and phosphoric esters of a carbohydrate, 
all closely associated wiih the cell and its nucleus. In 
foods, phosphorus occurs in the same positions, that is, 
inorganically or combined with protein, fat or carbohy- 
drate. It is not entirely proved but is very probable that 
the phosphorus in organic combination has the greater 
metabolic value, inasmuch as there is greater storage of 
nitrogen and stimulation of tissue gro^ih on foods con- 
taining phosphorized proteins, fats, etc. It has been 
shown, however, that the animal body can satisfactorily 
supply its phosphorus requirements by inorganic phos- 
phates. The omnivorous diet, even the widely varied diet 
of man, is very often deficient in phosphorus, a fact which 
becomes very important when we consider that the 
omnivorous diet produces many acid residues which must 
be neutralized, and that phosphorus is largely responsible 
for the maintenance of tissue neutrality. Voit showed 
that the phosphates excreted during starvation were 
