382 ASCORBIC ACID 



b. Growth Measurements 



(1 ) Increase in Weight of Whole Animal. An approximately normal growth 

 is obtained in young animals with a daily intake of 0.5 mg. of the vitamin. 



(2) Growth of Certain Organs or Tissues, e.g., Teeth, (a) Macroscopic Evi- 

 dence. Dalldorf and ZalP^ found that the rate of growth of the teeth is pro- 

 portional to the vitamin C intake. The rate of tooth growth was determined 

 by clipping off the exposed portions of the lower incisors at periods varying 

 from 20 to 90 days. The method was recommended as being more accurate 

 than the gross symptom procedure and much simpler than the microscopic 

 technique of Hojer.^^ The rate of dentine deposition in animals given 5 mg. 

 of ascorbic acid daily coincided with that of animals given greens and was 

 considered normal. 



(b) Microscopic Evidence. The effect of lack of vitamin C is shown by 

 early changes in the structure of the teeth. Variations occur in shape and 

 arrangement of the odontoblasts and their products, dentine and preden- 

 tine. 



The rate of growth of dentine may also be used in determining the mini- 

 mum protective dose. By staining the dentine wdth periodic injections of 

 alizarin the rate of dentine deposition was studied in relation to the intake 

 of vitamin C.^"* After a depletion period of 7 days the amount of dentine 

 deposited in the formative end of the tooth was found to vary directly with 

 the vitamin C intake. The rate of deposition of dentine in guinea pigs given 

 5 mg. of ascorbic acid coincided with that of animals given greens and was 

 considered as normal. 



Measurement of the rate of growth of the odontoblasts has proved to be 

 an especially accurate method. Crampton et al.'^- ^^ found that a considerably 

 smaller number of animals was required to obtain significant differences 

 between experimental groups than with the "increase in weight" method. 

 A 2-mg. daily dosage was shown by this method to give protection. 



The tooth shows a close relation to the level of vitamin C intake.'^- ^*"^^ 

 The advantages of the microscopic tooth methods for determining the mini- 

 mum protective dosage are their specificity and the shortness of the test 

 period. Because the microscopic changes in the teeth occur much earlier in 

 the deficient animals than do the macroscopic symptoms, twice as much 

 (presumably 1 mg.) antiscorbutic substance was found to be required by 

 the microscopic tooth method. ^^' ^^ Later, other workers reported a still 



12 G. Dalldorf and C. Zall, J. Exptl. Med. 52, 57 (1930). 



13 J. A. Hojer, Acta Paediat. Suppl. 3, 8 (1924). 



" P. E. Boyle, O. A. Bessey, and P. R. Howe, Arch. Pathol. 30, 90 (1940). 



15 S. S. Zilva and F. M. Wells, Proc. Roy. Soc. (London) B90, 505 (1919). 



16 S. B. Wolbach and P. R. Howe, Arch. Pathol. 1, 1 (1926). 



1^ L. Jackson and J. J. Moore, J. Infectious Diseases 19, 478 (1916). 



18 M. Goettsch, Quart. J. Pharm. 1, 168 (1928). 



19 W. H. Eddy, Am. J. Public Health 19, 1309 (1929). 



