182 The Unity of the Organism 



by the adrenal secretion simultaneously liberated, will drive 

 the blood out of the vegetative organs of the interior, which 

 serve the routine needs of the body, into the skeletal muscles 

 which have to meet by extra action the urgent demands of 

 struggle or escape. But there are exceptions to the general 

 statement that by adrenin the viscera are emptied of their 

 blood. It is well known that adrenin has a vasodilator, not 

 a vasoconstrictor, action on the arteries of the heart; it is 

 well known also that adrenin affects the vessels of the brain 

 and the lungs only slightly if at all. From this evidence 

 we may infer that sympathetic impulses, though causing 

 constriction of the arteries of the abdominal viscera, have 

 no effective influence on those of the pulmonary and intra- 

 cranial areas and actually increase the blood supply to the 

 heart. Thus the absolutely and immediately essential or- 

 gans — those the ancients called the 'tripod of life' — the 

 heart, the lungs, the brain (as well as its instiTiments, the 

 skeletal muscles) — are in times of excitement abundantly 

 supphed with blood taken from the organs of less importance 

 in critical moments." And Cannon concludes with the very 

 pertinent remark: "This shifting of the blood so that there 

 is an assured adequate supply to structures essential for the 

 preservation of the individual may reason abh^ be inter- 

 preted as a fact of prime biological significance." ^- Indeed 

 so ! Even more significant, I believe, than Cannon has shown 

 us — as we shall see in a later chapter. But the limitations 

 set at the outset of tliis chapter, namely that of dealing 

 only with neural processes strictly, especially as these mani- 

 fest themselves in reflexes, permits us to go no farther than 

 to call attention to the fact that while Cannon finds "the 

 most significant feature" of the reactions he has studied to 

 be "that they are of the nature of reflexes — they are not 

 willed movements, indeed they are often distressingly be- 

 yond the control of the will," ^'^ he yet has coupled them in 

 the most positive way with the emotions, especially with 



