42 PHYSIOLOGY AND NATIONAL NEEDS 



elusion seems to be inevitable that in some way — 

 on lines perhaps not yet fully cleared up — rickets 

 arises when fat-soluble vitamine is deficient in the 

 food. Other factors, such as a generally deficient 

 hygiene, may be contributory, but I for one am 

 quite convinced that the dietetic error is the primary 

 cause. No whit less important is the fact demon- 

 strated by Mrs. Edward MeUanby that deficient diets 

 such as those which induce rickets, also involve 

 grave errors in the growth of teeth in young animals. 

 We have had little suspicion until lately that the 

 quality of the fat supply in the diet could have an 

 efiect such as this. 



As a fat rich in the vitamine and capable of 

 preventing rickets in dogs, cod-liver oil stands pre- 

 eminent. It has been long known that the oil 

 favourably influences the course of rickets in infants, 

 a fact discovered empirically and without knowledge 

 of vitamines ; but a successful therapeutic measure 

 is much more likely to gain general credence and 

 to establish itself in practice if a rational basis for 

 it is made clear. Moreover, the recent attention 

 given to the importance of qualitative factors in 

 food has led to the use of cod-liver oil in the preven- 

 tion of rickets with successful results. These bring 

 observations upon human infants directly into line 

 with Dr. Mellanby's experiments. The following 

 are striking figures relating to infants in a negro 

 community of the United States. In this community 



