758 FREDERICK S. HAMMETT 



pressor response is due to a substance contained in the posterior lobe of 

 the hypophysis and its extracts. It should be noted that the type of pres- 

 sure increase produced by posterior lobe extracts is different from that 

 observed after the administration of epinephrin in that it is maintained 

 at a high level for a much longer period of time as demonstrated by Mum- 

 mery and Symes (1908) and Bell and Hick (1909). 



The question as to whether or not the point of attack of the effective 

 substance is the peripheral mechanism, the central nervous system or the 

 heart itself is still an open question with the evidence tending towards 

 the broader view of Wiggers (1911) that all are involved. He considers 

 that the slowing of the heart occurring synchronously with the rise in 

 blood-pressure is an indication of the stimulation of the cardio-inhibitory 

 center. Werschinin (1913), Tigerstedt and Airila (1913), Claude<, Porak 

 and Routier(a)(&) (1913), Wiggers (1911), Airila (1914) and others, 

 present evidence from various angles which effectively support Howell 

 (1898) and Schafer and Vincent (1899) in the opinion that there does 

 occur a generalized constriction of the peripheral arterioles. Nevertheless, 

 Frohlich ?nd Pick(fr) (1913) and Hallion (1914) have reported experi- 

 ments which tend to show that on certain parts of the vascular system, such 

 as the pulmonary artery, there may be produced a hypotensive instead of a 

 hypertensive effect. The lower cardiac activity, combined with the lesser 

 amount of blood in the peripheral vessels, led Claude and Porak(&)(&) 

 (1913) to the opinion that the action was a selective toxic one on the myo- 

 cardium. Werschinin (1913), Tigerstedt and Airila (1913), Wiggers 

 (1911) and others seem to coincide in this opinion as far as the second 

 phase of the reaction is concerned. This belief is supported by the observa- 

 tions of Etienne and Parisot (1908) and Hofstatter (1919) who found that 

 repeated injections of posterior lobe extracts resulted in cardiac hypertro- 

 phy, while Bauer and Aschner (1919) were unable to demonstrate that the 

 permeability of the blood vessels themselves was affected. That the pressor 

 action is mediated by a specific substance contained in the extracts and is 

 not dependent upon any secondary reaction induced through the liberation 

 of epinephrin from the adrenals, as indicated from the studies of Porak 

 (1913), is shown by the fact that Hoskins and McPeek (1913-14). obtained 

 the characteristic rise of blood-pressure on injection of posterior lobe 

 extracts when the adrenal veins were occluded. Hecht and Nadel (1913) 

 made a preliminary study of the phenomenon using the electrocardio- 

 graph but their results were not sufficiently numerous to allow any definite 

 conclusions to be drawn therefrom. Whether the primary point of 

 attack of the pressor substance is the neural mechanism or the muscular 

 mechanism of the vascular system is as yet undetermined. The initial 

 tachycardia observed by Claude, Porak and Routier (1913) and the 

 hypertrophy induced by repeated injections as described by Hofstatter 

 (1919) could as well be indicative of a neural stimulation as of a muscle 



