THE PRESIDENTIAL ADDRESS. 29 
rickets to be caused by improper feeding, though opinions differed as to the 
exact nature of the dietetic defect. The conclusion, first put forward by 
Mellanby in 1918, that a deficiency of fat-soluble vitamins plays a most 
important part in the causation of the disease is now generally accepted. 
This has been established by a large amount of work, both experimental 
and clinical, carried out by Mellanby himself, McCollum and Hess and their 
respective co-workers in the United States, and Korenchevsky and others 
in England. It may be laid down that if a young animal is supplied with a 
sufficiency of these vitamins, rickets will not develop. The question of 
prevention is therefore one of economics. The difficulty is that these fat- 
soluble vitamins are chiefly found in such food-stufis as butter, eggs, the 
fat of beef and mutton, and fish oils, all expensive articles of diet which the 
poorer classes can seldom afford. The only ‘ butter’ used by them is 
probably some form of margarine, made from vegetable oils which contain 
little or no anti-rachitic vitamin. The question of prevention is for the 
sociologist. Science can only discover the causes and point the means. 
It is for governments and local authorities to carry out preventive measures 
in practice, and it is to be feared that science is often far ahead of the 
community in its share of the work. 
Although the theory that rickets is an infectious disease has been 
exploded, a great and remarkable truth was contained in the domestication 
and hygienic theories which held that, among other unhygienic conditions, 
want of sunlight was concerned in the etiology of the disease. During the 
last five years it has been discovered that exposure to sunlight or to the 
ultra-violet rays of the mercury vapour quartz lamp can cure rickets in 
children. Experiments on animals have shown that the effective rays in the 
sunlight are also the ultra-violet. This discovery has indicated lack of 
sunlight during winter as one factor concerned in the large spring incidence 
of the disease in industrial cities in northern climates. 
A complete and well-controlled research showing the interaction of diet 
and light in the prevention and cure of rickets in infants was gained in 
Vienna, since the war, by Dr. Harriette Chick of the Lister Institute and 
her four colleagues. There the curious fact came to light that infants fed 
on a diet deficient in anti-rachitic vitamin developed the disease only in 
winter and not in summer, and, moreover, could be cured in winter by 
exposure to artificial forms of radiation or by administration of cod-liver 
oil without any other change in diet or management. Another set of children 
who had a sufficient supply of fat-soluble vitamins in their diet, in the form 
of cod-liver oil, escaped the disease altogether. 
