NUTRITION AND GROWTH 621 



vitamin. Lard does not contain it, so that young animals fed with this 

 as the only fat of an otherwise perfect diet fail to grow as shown in 

 Curve I, Fig. 186. An important difference will be observed in this 

 curve from that of II in which the factor B (antiberiberi vitamin) is 

 alone deficient, namely, that a small amount of growth continues for a 

 time after the removal of the proper diet. This indicates that there must 

 be some reserve of the fat-soluble vitamin in the body, and it is only 

 after this is exhausted that growth entirely ceases and decline then sets 

 in. Further evidence of tissue storage of this vitamin is afforded in 

 Curve IV in which the upper curve represents the normal growth of 

 young rats, the lower, of those nursed by a mother receiving a diet that 

 was deficient in the vitamin. 



When the reserves of the fat-soluble vitamin are exhausted, not only 

 do the young animals fail to grow, but they become highly susceptible to 

 bacterial disease, one symptom of which is a very characteristic eye in- 

 fection (xerophthalmia) which begins with a swelling of the lids, and 

 later develops into a purulent conjunctivitis, often leading to blindness. 

 Administration of some fat-soluble vitamin in the diet dispels the eye 

 symptoms usually within a few days. When the dietary of adult ani- 

 mals contains none of this vitamin, the eye symptoms also develop, 

 the general condition greatly deteriorates and the animals become ex- 

 tremely susceptible to bacterial infections, particularly those affecting 

 the lungs, and from which they readily succumb. Adults are, however, 

 much less susceptible to the absence of the fat-soluble vitamin than 

 growing animals. This may be because of great storage capacity for it 

 and is shown in Curve III of Fig. 186. 



At the same time it is worthy of note that there is reason to believe 

 that the condition known as war edema is due to a deficiency of this 

 vitamin. It may be stated here that when both the A and B factors 

 are absent from the diet young animals immediately cease to grow and 

 develop the nervous symptoms due to the absence of the B factor, from 

 which they usually succumb before the symptoms due to the absence of 

 the A factor have had time to develop. 



It is believed that it is with the metabolism within the cells rather 

 than with that of fat itself that the fat-soluble vitamin is concerned. 



A most important relationship probably exists between this vitamin 

 and the occurrence of rickets. Thus when the puppies of large dogs are 

 fed with separated milk, bread, linseed oil, yeast and orange juice, they 

 grow at a normal rate, but in about six weeks develop undoubted symp- 

 toms of rickets (bones defectively calcified so that the long bones bend, 

 swelling at the epiphyses, a rosary at the costochondral junctions, the 

 ligaments loose, general lethargy and loss of muscular tone). In this 

 diet both the water-soluble and the antiscorbutic factors are present in 



