From the point of view of general physiology, Evans's summary1 of the rapidly increasing evidence that carbon dioxide can be utilized by higher animal tissues represents an important fundamental advance in current nutritional theory. Certainly it throws doubt on the validity of certain accepted clinical diagnostic methods.
For decades a sharp differentiation has been made between plant and animal nutrition, based on their basic nutritional requirements. Plants, with their ability to use simple inorganic substances such as carbon dioxide, ammonia and water, have been placed in one category, sharply separated from animals, which apparently require more highly complex preformed dietary constituents. Experimentally it has been shown that the carbon requirements of higher plants can be satisfied completely by photosynthetic uptake of carbon dioxide. In animals carbon dioxide is traditionally regarded solely as a nonrecoverable metabolic end product.
The first serious break with this tradition dates from the demonstration by
UTILIZATION OF CARBON DIOXIDE BY ANIMAL TISSUES. JAMA. 1942;120(6):454. doi:10.1001/jama.1942.02830410042012