VITAMIN A 281 



ing the weakening of the tissue. Goldblatt and Benischek (1927) and 

 Tyson and Smith (1929) have confirmed the epthelial metaplasia as 

 resulting directly from the vitamin A deficiency. Infection was uni- 

 versally present, and in the more severe cases dominated the picture. 



Following corrective dietary treatment the xerophthalmia healed 

 more quickly than the other lesions. Abnormal conditions of the epi- 

 thelium and chronic or acute infection persisted in the tongue and 

 renal pelvis after the rat outwardly appeared healthy. 



Falconer (1926), referred to the report of Cramer, Drew and 

 Mottram (1922) that vitamin-A deficiency diminishes the platelet count; 

 but from his own work concluded that, "Changes in the relative number 

 of platelets, red cells, and white cells in the blood of rats are not 

 striking enough, or constant enough, to constitute specific lesion of 

 vitamin-A deficiency in these animals." Falconer also considered the 

 work of Bedson and Zilva (1923) to be in agreement with his own, 

 the greatest diminution which they found being 21.3 per cent. 



Cramer and Kingsbury (1924) tested the blood of vitamin-A-de- 

 ficient rats for ability to develop agglutinins against various micro- 

 organisms and found no loss in agglutinating power. They concluded 

 at this time that a deficiency in vitamin A does not diminish the effi- 

 ciency of the general humoral defenses of the body, but only of the 

 local tissue defenses. "Under the ordinary conditions of vitamin experi- 

 ments, the breaking down of local defenses allows access to the com- 

 paratively avirulent bacteria which normally inhabit the intestine, the 

 respiratory tract or the conjunctival sac, so that the resulting infec- 

 tions are as a rule avirulent in type. When organisms of a more virulent 

 type are present, the condition of the local defenses rather than the 

 mere presence of these organisms may be the factor which determines 

 the onset of a virulent infection." 



Turner and his associates (Turner, 1928, 1929; Turner, Anderson, 

 and Loew, 1930) in studies of the bacterial flora of the various organs 

 of rats in which lesions are most frequent as the result of vitamin A 

 deficiency encountered types of pathogenic organisms in increasing 

 frequency with increasing severity of the symptoms of A deficiency 

 and concluded that "these organisms gain a pathogenic hold during 

 the depressed state of their host resulting from vitamin A deficiency." 



Further emphasis on the role of vitamin A as an anti-infective 

 agent was given by Green and Mellanby (1928) in tabulated data show- 

 ing the incidence of lesions and infections in various organs of rats 

 suflFering from vitamin A deficiency. Among the entire number of 

 93 vitamin-A-deficient animals examined, all showed lack of adipose 



