GROWTH AND NUTRITION 79 



The other pigs were given a diet of milk and wheat middlings, 

 and were soon restored to a normal condition. 



The other groups all made fair gains, though there was one 

 exception in each of the groups, 2 and 3. As would be expected, 

 all the variations in phosphorus content were in the bones; there 

 were none in the fleshy tissue. It is now the general opinion 

 that inorganic phosphorus can meet all the requirements for 

 that element. We may also say that, with one exception, it 

 is unnecessary to supply any of the mineral elements in organic 

 combination. This exception is sulphur, due to the fact that the 

 animal organism is unable to synthesize the sulphur-containing 

 amino acid, cystine. 



Numerous investigations have been made concerning the ef- 

 fect of a deficiency of calcium on the rate of growth. It is quite 

 certain that if the ration is sufficiently low in calcium, and if the 

 animals are sufficiently immature when placed on the diet, 

 growth will be inhibited. It is, however, quite remarkable to 

 what an extent an animal will grow on a ration deficient in cal- 

 cium, provided all other factors are satisfactorily adjusted. 



For example Voit 13 reports that if rations low in calcium are 

 fed, growth will be normal if the ration is otherwise adequate. 

 According to this observer the chief effect of a ration low in cal- 

 cium is to produce a condition resembling rickets. A somewhat 

 similar observation was made many years later by Aron and 

 Sebauer. 14 They fed one group of dogs on a ration high in cal- 

 cium and another group on a ration considerably lower in this 

 element. Although the group receiving the ration low in cal- 

 cium developed marked symptoms resembling rickets, both 

 grew at practically the same rate. It is also worthy of note that 

 there was some interference in locomotion of these animals and 

 there were other symptoms of general malaise. This sort of in- 

 vestigation has been continued by Eckles and collaborators. 15 

 They began with two Jersey heifers about six months of age, 

 which had been reared on a normal diet. One of these was 



