Bodily changes in pain, hunger, fear, and rage — Inside the Classic

Experimental Evidence and the Splanchnic Nerves

The core of the book rests on laboratory data, much of it presented in tabular form. In one series of experiments, Cannon measured blood coagulation time in cats before and after stimulating the splanchnic nerves. A typical record shows clotting dropping from 4.5 minutes to 2 minutes immediately after stimulation, then gradually returning. Cannon notes that 'the degree of acceleration is not so great after the second stimulation'—a pattern of diminishing effect he observed repeatedly. By surgically removing one adrenal gland and stimulating the nerve on that side, he demonstrated that the hastening of coagulation depends on the adrenal glands: without the gland, stimulation produced 'no shortening of the coagulation time.' These controlled comparisons form the evidentiary backbone of his argument.

The Role of the Adrenal Glands in Bodily Response

Cannon's experiments isolate the adrenal glands as critical intermediaries. He cites Elliott's finding that 'in the cat the splanchnic innervation of the adrenals is not crossed,' meaning each nerve supplies only the gland on its own side. By stimulating the left splanchnic after removing the left adrenal, and then the right splanchnic with the right gland intact, he produced a clear contrast: no clotting change on the glandless side, a sharp acceleration on the intact side. This methodical approach—using the same animal as its own control—strengthens his conclusion that nerve impulses act through adrenal discharge rather than directly on other organs. The text repeatedly returns to this mechanism as a key to understanding how emotional excitement prepares the body for action.

From Laboratory to Behavior: Interpreting the Findings

Cannon frames his physiological results as having broad implications for understanding 'the action of men and beasts.' He treats the bodily changes not as mere correlates of emotion but as functional adaptations—responses that 'are nicely adapted to the individual’s welfare and preservation.' The preface explicitly states that a 'knowledge of the conditions which attend these experiences' is 'of general and fundamental importance in the interpretation of behavior.' However, the excerpts provided focus almost entirely on the experimental data; the book's later interpretive chapters are not included. Readers should note that Cannon's conclusions about the evolutionary purpose of these responses are inferences drawn from controlled animal experiments, not from human behavioral studies.

Cannon's work is best approached as a research monograph rather than a popular science book. The dense tables and repeated measurements reward careful reading, especially the comparisons between stimulated and unstimulated conditions. Readers interested in the history of physiology will find a clear example of early 20th-century experimental design, while those seeking psychological insights should note that the book's claims about emotion are grounded in specific, measurable bodily processes—not introspective reports.

I have often thought of Cannon’s watchful study—how the body prepares itself for danger—in the same breath as a quieter old guide, Making Good on Private Duty: Practical Hints to Graduate Nurses — Text and Context, for both were written by caring hands observing the tremor beneath calm duty. There is a shared warmth in their careful noticing, as if each remembers the same midnight vigil.