using the destruction increased 90 to 95 per cent. These particular observations seem to confirm the view of Harden and Zilva that the vitamine is especially sensitive to alkali. Hess has recently reported that oxygen is destructive to this vitamine. IV. PHYSIOLOGICAL PROPERTIES OF THE "A" VITAMINE Most authorities are now agreed that both the "A" and "B" types are essential to growth. Rohmann still holds out against the vitamine hypothesis. McCollum has recently pointed out that while rats do not have scurvy it does not at all follow that the absence of the "C" in their diet is immaterial, but that the contrary is true. Failure to grow, then, may manifest itself as a result of the absence of either of the first two types and possibly is affected by the absence of the "C." We have already seen how this failure may be utilized to measure the vitamine content of a source. The absence of the "A" type however may also manifest itself in another way, viz., by the development of an eye disease which McCollum first designated as xerophthalmia or dry eye and which the British authorities prefer to designate as keratomalacia. The failure of this result to always follow the absence of the "A" type in the diet has led some to question the specificity of this disease. While the infection of the eye is due to other agents the sum of the evidence supports McCollum and points to the absence of "A" as the true predisposing cause of the disease. Bulley, basing her claims on a study of some 500 rats fed on a synthetic diet, claims that the eye condition is not primarily due to a dietary deficiency but to an infection resulting from poor hygienic conditions. In reply to her contentions Emmett has reviewed his own data and presents them in the following summation: _________________________________________________________________________ | | | | RAT | KIND OF VITAMINE | NUMBER CASES | POSITIVE CASES | PER CENT GROUPS | ABSENT IN THE RATION | REPORTED | OF XEROPH- | POSITIVE | | | THALMIA | _______|______________________|______________|________________|__________ | | | | A | Fat-soluble "A" | 122 | 120 | 98 B | Water-soluble "B" | 103 | 0 | 0 C | None | 216 | 0 | 0 _______|______________________|______________|________________|__________