VITAMIN C 177 



same extracts after destruction of vitamin C. Of various phenols tested, 

 quinol alone was said to give the blue color. Kay and Zilva (1923) 

 applied the test to a large number of substances which were tested 

 simultaneously on guinea pigs and found the relationship not to hold 

 true in all cases. Some antiscorbutically active substances failed to 

 give the color reaction and other inactive substances gave a positive 

 reaction. Wedgewood and Ford (1924) also reported a lack of spe- 

 cificity in the test. In later papers Bezssonoff (1924a, 1924b, 1926) 

 outlined various conditions which must be fulfilled to obtain satisfac- 

 tory results, but the method has never received much favor. 



Hojer (1926) proposed a new method based on the histological 

 changes in the teeth of guinea pigs on diets deficient in vitamin C. 

 Since changes are observable in the teeth earlier than in any other 

 part of the body, the feeding period is considerably shortened, from 

 10 to 14 days being considered sufficient. 



The technique as originally described by Hojer is as follows: "As 

 previously, young guinea pigs from a certain day on are given a basal 

 diet free from antiscorbutic, but otherwise complete, and to this diet 

 are added quantitatively daily doses of the juice to be examined. For 

 a sharp determination of the fully protective dose it is advisable to 

 have several animals on different doses. In addition there ought to be 

 two control animals on the basal diet alone, and two on the basal diet 

 with a fully protective dose of a known antiscorbutic. After a period 

 of 10-14 days all the animals are killed. The one-half of the lower jaw 

 is taken out and decalcified in a 5 per cent tri-chloracetic acid solution. 

 It is then embedded and sectioned after one week. The section is made 

 through the foremost molar at right angles to the longitudinal axis of 

 the jaw. Some sections are stained with haematoxylin-eosin, and others 

 with tri-oxyhaematin according to the method of Hansen." 



The principal examination is made of the cross section of the incisor 

 roots. It is stated that on a fully protective antiscorbutic dose the section 

 stained with hematoxylin-eosin shows a broad uniformly stained pink 

 layer of dentin, a white uncalcified predentin, a layer of long, slender 

 parallel odontoblasts, and a pulp of star-shaped cells. When about 0.9 

 of the minimum protective dose of vitamin C is given, the odontoblast 

 layer is distinctly narrower; with still less, the uniformity of the dentin 

 staining has disappeared, the freshly made dentin having a lighter 

 color and less collagen. When vitamin C is completely lacking the dentin 

 is rather thin, the predentin is stained very dark because it is calcified, 

 the odontoblasts no longer exist as a continuous layer. "They seem 

 to be on a disordered march into the hyperemic pulp and do not 



