GROWTH AND NUTRITION 81 



corn, and brewers' offal. For the first three or four weeks after 

 farrowing, the pigs seemed normal, but after that time deaths 

 became numerous and post-mortem examinations revealed a 

 variety of pathological conditions. The blood was much lighter 

 in color than is normal and the count of red corpuscles was re- 

 duced to about three million per cmm. It seemed probable that 

 the trouble was due to the lack of iron in the ration, so this was 

 supplied in the form of ferric oxide. As a result the younger 

 pigs developed no symptoms of the disease, and many of the 

 affected animals recovered. There was also an increase in the 

 hemoglobin content of the blood. 



In regard to the more obscure mineral elements the best data 

 we have are those obtained by Osborne and Mendel. 1 ' Their 

 work was made possible by the recent discovery of the vitamins, 

 and so the use of synthetic diets, composed of comparatively 

 pure nutrients relatively free from inorganic contamination, was 

 followed. Complex salt mixtures were then prepared, each free 

 from some one of the elements to be investigated. These ele- 

 ments were as follows: sodium, potassium, magnesium, chlor- 

 ine, calcium, and phosphorus, singly and in combination. The 

 appended charts bring out some very striking facts. It will be 

 noted that the quantity of magnesium, chlorine, sodium, and 

 potassium for normal growth is very small indeed. A diet con- 

 taining o.O i per cent of magnesium, 0.03 per cent of potassium, 

 and less than 0.04 per cent of either sodium or chlorine per- 

 mitted normal growth. The one exception noted was a simul- 

 taneous reduction of both sodium and potassium. When both 

 were decreased at once, growth stopped. Later, sodium only was 

 added without much improving the rate of growth. Potassium 

 was then substituted for sodium, and growth was resumed at a 

 rapid rate. These observations, of course, do not indicate that 

 these elements are not required, merely that they are husbanded 

 with extraordinary tenacity. The quantity of chlorine that must 

 be fed is very small, but if the gastric juice, containing hydro- 

 chloric acid, is removed, the results are speedily disastrous. 



