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M.—AGRICULTURE. 207 
in complete starvation. Signs of disturbance of the digestive organs 
appeared early. They were soon accompanied by increased excitability 
and weakness of the neuro-muscular system. The central nervous system 
was also affected, as was shown by the occurrence of convulsions and 
_ periods of drowsiness. A remarkable feature of these experiments was 
the profound disturbance caused by relatively small losses of inorganic 
salts from the system. The total mineral matter of the body at the begin- 
ning of the feeding with the salt-free diet was estimated at 1,500 grams. 
Phosphoric acid and sodium chloride were lost in greatest amounts, and of 
these only about thirty grams and seven grams respectively were lost 
before death occurred. A well-nourished body could lose a far larger 
proportion of its total protein, fat or carbohydrate without showing any 
marked disturbance of its functions. 
A number of workers have studied the results of prolonged feeding 
of a diet containing a marked excess of acid radicles, and have found 
that, under such conditions, the body tends to be depleted of bases, and 
when a certain stage of depletion has been reached, there appear signs of 
disturbance of the functions of the digestive and nervous systems and 
loss of weight. The regulating mechanisms of the body, however, are 
able to deal with a considerable excess of acid in the food, and opinion is 
divided as to the extent to which, in actual practice, excessive acidity of 
the diet is a factor in causing malnutrition. It is probable that, if evil 
effects do occur, they will be most marked during the period of active 
growth, because an excess of bases is required for tissue construction. 
Deficiencies of single elements, or of groups of elements, in the diet, 
are followed by more or less characteristic symptoms, which, however, are 
_ modified by the presence or absence of other factors. It is interesting 
_ to note that, in many cases, the pathological symptoms due to deficiency 
of individual elements, such, for example, as the hyper-excitability which 
occurs in calcium deficiency, can be explained by the influence of the 
ion concerned on the colloids of the tissues or on the permeability of 
_ membranes. 
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Under experimental conditions it is possible by feeding diets with 
marked deficiencies or excesses of some of the mineral elements to produce 
conditions of malnutrition which are so definite and marked that they 
are as easily recognised as definite diseases; indeed similar conditions 
occurring in practice are regarded as definite diseases. Thus, primary 
anemia, simple goitre and rickets are produced by deficiency of iron, 
: 
: 
iodine and either calcium or phosphorus respectively. An interesting 
case of a disease due to an excess of a mineral element is reported by 
“McCollum, who regards an inflammatory condition of the eyes, resembling 
xerophthalmia, which he calls ‘ salt ophthalmia,’ as due to excess of 
chlorine in the food. 
In addition to these diseases due to excesses or deficiencies of mineral 
elements in the diet, in which the symptoms form a definite and easily 
recognised picture, and the cause is admitted, there are conditions of 
malnutrition due to the lack of balance of the mineral elements in the diet, 
where the signs are much less obvious. In young animals there may be 
retarded growth without any definite pathological symptoms. The only 
reason for supposing that such animals are not in a perfect state of health 
is that their rate of growth is not optimal, as is shown by the fact that 
