208 THE PITUITARY, THYROID AND ADRENALS AS A SYSTEM. 



E. de Cyon, 44 after an exhaustive experimental study of 

 the pituitary gland, reached the conclusion that this organ, like 

 the thyroid, possessed two functions: the one mechanical and 

 the other chemical. Unaware, of course, of the role played by 

 the suprarenal gland as given in the present work, he care- 

 fully recorded the effects of mechanical pressure upon or elec- 

 trical stimulation of the pituitary. He found that either of 

 these sources of irritation immediately gave rise to variations 

 of blood-pressure and to a notable increase of power and slow- 

 ing of cardiac action, and ascribed these phenomena to excita- 

 tion of the vagus, which nerve was supposed by him to cause 

 vasodilation of the thyroid, followed, in turn, by depletion of 

 the cerebral circulation. 



From our standpoint it seems more probable, as we have 

 seen, that an entirely different process occurs: i.e., that the 

 pituitary directly stimulates the suprarenal glands. Even in 

 this connection, however, de Cyon's experiment is a valuable 

 one, especially when connected with one performed by Howell 

 with pituitary extract and which showed that extract obtained 

 from the posterior lobe alone contained the blood-pressure- 

 raising substance. While de Cyon's observation enables us to 

 distinctly prove a direct connection between the pituitary body 

 and the adrenals, Howell's suggests that the posterior lobe must 

 be the one functionally connected with the latter organs. In- 

 deed, so marked was the suprarenal stimulation thus produced 

 that, although unaware that he was witnessing effects of supra- 

 renal origin, the resemblance suggested itself to him. Thus, he 

 says: "These extracts injected into the normal animal with its 

 vagi intact cause a very pronounced slowing of the heart-beat, 

 similar to that caused by suprarenal extracts, but lasting a much 

 longer time. The heart-beat is not only slowed, but is consid- 

 erably augmented in force, as is shown by tracings taken with 

 a Hiirthle manometer/' 



If the anterior lobe does not contain a substance capable 

 of producing similar effects, what can its functions be? It 

 seems disconnected from the posterior in this particular, though 

 related with the infundibular walls by connective tissue and 



** E. de Cyon: Archives de Physiologie, July. 



