758 REPORT—1904. 
was found to be wholly free from potassium. The medulla, on the other hand, 
may contain considerable quantities of it irregularly distributed, and some may be 
found between the axon and the sheath. 
5. The protoplasm of smooth muscle fibre is almost free from potassium, 
but the doubly refractive substance in the dim bands of striated muscle is rich 
in it, 
6. The granular zone in ferment-forming cells (pancreas) is rich in potassium, 
while the remainder of the cytoplasm is free from it. When the granular area 
diminishes through secretion there is apparently a concurrent diminution in the 
potassium-holding area. 
7. All dead and inert material in a living tissue becomes charged with potas- 
sium. This is particularly the case with intercellular material. 
8. The intestinal epithelial cells in vertebrates and invertebrates excrete 
potassium, 
5. Investigations on the Nutrition of Man. 
By Professor W. O. ATWATER. 
The author gave an account of the inquiry regarding the food and nutrition of 
man which is carried out in the United States by authority of Congress. The 
work is done by co-operation between the Department of Agriculture and a large 
number of universities, experiment stations, and other organisations from Maine 
to California. The Federal Government devotes 20,000 dollars (4,000/.) a year 
to the enterprise. This is used mainly as aid to research, and is supplemented 
by grants of money and other aid from State Governments and other sources. 
The inquiry has three aspects—one very practical, another more purely scientific, 
and a third educational. 
On the practical side, studies are made of the composition, the digestibility, 
and the nutritive values of food materials commonly used in the United States. 
This is done by chemical analyses and by actual experiments with men. Invyesti- 
gations are also made of the kinds, amounts, and costs of the food consumed by 
people of different classes and occupations in different parts of the country. The 
results throw valuable light upon the physiological, hygienic, and economic 
phases of the subject. At the same time experiments are made on various 
collateral topics, and thus information of the greatest usefulness is being acquired. 
The more abstract scientific researches have to do with the transformations of 
matter and energy in the body, and consequently with the fundamental laws of 
nutrition. The experiments are made with men by use of the respiration calori- 
meter, an apparatus which serves to measure the changes which take place in the 
body with different diets and under different conditions, as, for instance, with 
physical or mental work or of rest. One very interesting result is the demon- 
stration that the law of the conservation of energy obtains in the living body. 
Such purely scientific research is difficult and costly, but the speaker insisted 
earnestly upon its fundamental importance. These experiments show very 
clearly how the demands of the body for energy, for warmth, and work decide the 
needs for food. Taken in connection with the practical inquiries, they reveal 
much that was previously unknown regarding the uses of food and the adaptation 
of diet to health, purse, and welfare. 
Numerous illustrations were given of the results of these inquiries. The 
average man on average diet digests and utilises about 96 per cent. of the material 
and 91 per cent. ofthe energy of his food, the rest being rejected in the excretory 
products; but the proportions thus utilised vary with the person, and still more 
with the food. The investigations bring out these differences in much detail. 
The question of the nutritive values of bread made from ordinary white flour 
as compared with the whole wheat meal or brown flour, such as is used to make 
‘brown bread,’ was considered. Chemical analysis shows that the bran which is 
removed in making the white flour contains considerable quanties of nitrogenous 
materials, and also of mineral matters, such as phosphates. A natural inference 
