Is coffee harmful then? What do physiologists, pharmacologists and medical men say? Coffee demonstrably enlivens the intellect, removes the sensation of fatigue and makes the subject feel more comfortable. These are gifts not to be sniffed out of court. But is coffee safe and harmless enough that we may dare indulge ourselves in this pleasant reaction in a world where the pleasant is so readily assumed to be _per se_ the invidious--and so often is actually so? The question is in dispute like most questions considered settled by many people. There is no more reason to conclude one way than the other in so far as average adults are concerned. All who say dogmatically “No coffee--it is very harmful” are as wrong as all who state the opposite of this. In his “Personal and Community Health” C. E. Turner says coffee is not harmful to most adults in reasonable quantities. G. N. Stewart’s “Physiology” remarks that tea and coffee are safe stimulants because they have no bad after effects. Stewart also cautions against their abuse, but it may as well be stated at once that the question of abuse introduces an altogether new factor. Water and salt are absolutely necessary to life but the abuse of either is injurious. We can produce true water intoxications and salt eaten to excess can do us much harm. All articles of diet from parsnips and lamb chops to caffeine and alcohol can harm if abused and we should assume when speaking of them a sane, rational use and regard abuse as a harmful condition of a different order altogether. As C. E. A. Winslow well says in his “Healthy Living”--“The fact that tea and coffee sometimes become tyrants does not mean that such drinks are necessarily bad.” In one thing medical authorities do agree, however, coffee and tea are not beverages for children. Moralists to the contrary notwithstanding, this is again beside the point when we are considering the reasonable use of coffee by adults. Adults and children are essentially different animals using their food intake differently--the one for upkeep and repair the other for new construction as well as upkeep and repair. They differ basically in metabolism. They have different metabolic rates and different expenditures of energy. The child is turning food into flesh and bone and blood at a much greater rate than a fully-grown adult organism is ever required to do. Diets which would amply sustain an adult may easily be detrimental to or deficient for young and growing children. We shall, then, restrict ourselves herein to the rational use of coffee by average adults. What can coffee, or its active principle caffeine, do to harm adults?