Transmission of information by the arterial blood stream with particular reference to carbon dioxide.

An estimate of the amount of information transmitted by way of the arterial blood stream in animals is made. Many assumptions are necessary to pose the problem in analyzable form. Taking carbon dioxide as a representative substance, a distribution of maximum entropy is developed. Three points emerge: (1) that homeostatic stability can be related to chemoreceptor sensitivity if both are given statistical interpretations consistent with concepts of information transmission, (2) that the heart acts as a filter which has considerable smoothing effect which depends in a specific fashion upon the cardiac residual volumes, and (3) a numerical estimate of channel capacity is made. The estimate is undoubtedly high. Assuming values typical of man, the calculated channel capacity for CO(2) is 3.5 to 4.7 bits per second. Since some sixty substances of communication importance occupy the blood stream simultaneously, the blood stream has a total capacity near 250 bits per second if every chemical modality has the same properties as CO(2).