326 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1944 
ering coward, and may be returned to its former state by pituitary 
injections. Injections of prolactin into rats with no trace of maternal 
instincts will fill them so full of mother-love that they will even mother 
baby squabs instead of eating them. One is led to interesting specula- 
tion as to whether injections of prolactin might not be a good alterna- 
tive to execution for despotic dictators. 
The hormones produced by the endocrine glands, some stimulating 
and some inhibitory, not only affect the body as a whole in many 
complex ways, but they interact with each other in such an intricate 
manner that we are still very far from ideal utilization of them, and 
we may look forward to a great extension in the future. Yet even 
now, only 50 years from the birth of the science, the use of hormones 
has revolutionized a large part of medical practice and has given new 
insight into many physiological processes, such as metabolic rate, 
sugar metabolism, blood pressure, menstrual disorders, psychotic mal- 
adjustments, adiposity, sexual aberrations, and reproductive difficulties. 
Now let us turn to another contribution of biology to medicine— 
knowledge of nutrition. For lack of time I will pass briefly over 
many interesting discoveries connected with metabolism of proteins, 
fats and sugars, utilization of minerals, etc., though in passing I 
must pause long enough to mention a relatively new tool in physiologi- 
cal research—the use of ions tagged by means of atoms of unusual 
weight or made radioactive in cyclotrons. By this means it has been 
found that molecules in the body, even those supposed to be relatively 
stable in bones, teeth, or fat, are forever being shifted about and re- 
placed by new ones. The body is even less stable than it was thought 
to be. 
The most significant discoveries in. nutrition, ranking close to the 
discovery of hormones in their importance to human welfare, were 
those of the vitamins. Since the days of leopard-skin dinner jackets 
and struggles with cave bears instead of dictators, man’s ways of 
life have undergone many changes and so have his foods. With the 
development.of agriculture and civilization his food became less varied 
and more highly manipulated. He began to live more extensively 
on grain, to store food for periods of famine, and to cook it. Later 
he began throwing away the vitamin-bearing parts of his cereals, 
developed a taste for refined sugar, protected himself from sunlight, 
and often lived for months without fresh fruits or vegetables. Beri- 
beri, scurvy, rickets, pellagra, and night blindness attacked whole 
populations. 
Except for the cure of scurvy by eating lemon juice or hemlock 
leaves some 200 years ago, nothing definite was known about these 
nutritional-deficiency diseases until Eijkmann began experimenting 
with diseased fowls in Java 45 years ago. Gradually during the last’ 
30 years a whole alphabet of vitamins has been discovered, but it is 
