In the foregoing there has been frequent reference to the close relationship between scurvy and the incidence of the infectious diseases--to the fact that a scorbutic condition increases the susceptibility to infection. This is indeed one of the most characteristic, as well as one of the most important phenomena associated with scurvy and other disorders resulting from vitamine deficiency. Mention has been made of the special susceptibility to the diphtheria bacillus, and to the organisms leading to coryza and the respiratory diseases, but no doubt this applies also to invasion by other bacteria. We wish, however, to confine ourselves to the nutritional disorders, first in their relationship one to the other, and second, as a group of deficiency diseases, due to a lack of vitamines of various kinds. As is well known, in addition to scurvy, this group generally includes beriberi, a disease attributed to a lack of the water-soluble vitamine, and xerophthalmia, an eye condition which recently has been brought about in rats by placing them on a diet free from fat-soluble vitamine. These, however, form only the nucleus of the disorders which commonly are included in this category. Schaumann, the first to formulate this classification, illustrated his conception of the interrelationship by depicting the various members as spokes of a wheel surrounding a central hub. He included scurvy, rickets, osteomalacia, typical beriberi, ship-beriberi, pellagra and mehlnaerschaden. Funk made a similar classification of disorders which he termed the "avitaminosen." There is a tendency to enlarge rather than to decrease the membership of this class, and recently war or hunger edema, infantile atrophy and diarrhoea, sprue, coeliac disease, leprosy and others have been proposed as suitable candidates. At the present time it is impossible to determine which and how many of this motley company should be associated with scurvy. Some, possibly, are the result of a lack of vitamine, but for the present it will be well to bear in mind that three vitamines only have stood the test of experiment, and only these three therefore can be definitely connected in a causal relationship with pathologic conditions. In addition to this consideration of the interrelationship of the "deficiency diseases," the kinship of allied disorders--more particularly of rickets--must be discussed.