THE CHIEF CENTER OF THE NERVOUS SYSTEM. 591 



THE POSTERIOR PITUITARY BODY AS THE CHIEF CENTER 

 OF THE NERVOUS SYSTEM. 



Howell, 60 in the course of experiments which led him to 

 conclude that "the infundibular lobe of the hypophysis (the pos- 

 terior pituitary) is, in all probability, not a rudimentary organ, 

 but a structure that has some important physiological activity," 

 found, as we have already stated, that "the extracts of the 

 glandular lobe (the anterior pituitary) have little or no per- 

 ceptible effect when injected alone. Extracts of the small in- 

 fundibular lobe, on the contrary, have a distinct and remark- 

 able effect upon the heart-rate and blood-pressure, an effect 

 which resembles, in some respects, and differs, in others, from 

 that shown by suprarenal extracts." 



We have seen in our previous analysis of these observations 

 that the symptoms produced were those of suprarenal over- 

 activity. In other words, the extract acted like a toxic; the 

 heart-beat was "not only slowed, but considerably augmented 

 in force," says Howell, "as shown by tracings taken with a 

 Hiirthle manometer," etc. When both vagi were cut or a 

 little atropine was given, the slowing of the heart was less 

 marked. The result of vagal section is evident. As to the 

 atropine, it prevented the slowing because it served to increase, 

 when added to the pituitary extract, the dose of toxics in the 

 blood, thus causing suprarenal insufficiency, instead of over- 

 activity. But an interesting query imposes itself in this con- 

 nection: The extract having, by its action upon the anterior 

 pituitary, stimulated the activity of the adrenals, how did the 

 former, through the increased oxidizing substance, bring about 

 increased vagal action? The answer is easily reached: the pos- 

 terior pituitary being also copiously supplied with blood, its 

 activity is likewise increased. This emphasizes an important 

 feature: i.e., the fact that the posterior pituitary is functionally 

 stimulated, as is any other organ, by the oxidizing substance in 

 the blood passing through it. Indeed, the nerve-fibers which 

 Berkley found to accompany the arteries suggest the presence 

 of a functional arrangement similar to that of any organ, while 



60 Howell: "Transactions of Congress of American Physicians and Surgeons," 

 vol. iv, p. 83, 1897. 



