106 IMMUNOT.OGY 



another subject over which there is a great deal of controversy. 

 As regards the experimental animal there is abundant evidence in- 

 dicating that this vitamin plays an important role in maintaining 

 in a normal healthy state the epithelial coverings of the body. 

 When animals are fed upon a diet deficient in vitamin A, there 

 results marked pathological changes in the cutaneous system, 

 epithelium of the eyeballs, paraocular glands and the respiratory 

 epithelium. These changes, among them being extensive keratiniza- 

 tion of the ocular and respiratory epithelium, are associated w^ith 

 a definite lowered resistance to invasion by pyogenic bacteria. 

 After infection is established, the feeding of vitamin A does not 

 result in a cure. Thus it would appear that its function is pre- 

 ventive in that it aids in maintaining a normal healthy epithelium 

 which is resistant to invasion. 



Whether vitamin A plays a similar role in man has been much 

 debated. In an interesting discussion of this subject Eusterman 

 and Wilbur (1932) present evidence bearing upon both sides of the 

 controversy. They are quite conservative and state that further 

 research is desired, yet they seem to think that it may play a pro- 

 phylactic role in man similar to the one it plays in the experimental 

 animal. For a more extensive discussion and a comprehensive 

 bibliography of the subject the student is referred to an excellent 

 symposiimi on vitamins (1932), to a discussion by Szent-Gyorgyi 

 (1939), a report by the Council on Pharmacy and Chemistry and 

 Council on Foods (1939) and to a paper by Maekie, Eddy and 

 Mills (1940). While these papers present many new facts about 

 vitamins, they throw very little light upon their role in immunity. 

 Nutrition and Resistance. — Anderson and Fraser (1934) have 

 studied the influence of nutrition on the natural immunity re- 

 actions of the blood and skin to bacterial toxins. They find that a 

 caloric deficient diet decreases both the hemolytic activity of sheep 

 serum toward rabbit erythrocytes and its complementing powers 

 but it increases the agglutinating power of serum for Br. abortus 

 (porcine). They find that intradermal toxin tests are not af- 

 fected either by a deficiency diet or by a diet which includes cod- 

 liver oil and calcium. 



In regard to the effect of diet on inborn resistance in mice in- 

 fected with B. enteritidis Webster and Hodes (1930, 1939) report 

 that altering the diet did not affect the spread of infection in a 



