348 THE DUCTLESS GLANDS 



There was no marked effect upon the rate of the heart-beat. 

 (See Figs. 96, 97.) 



Howell made a considerable step in advance. He divided 

 the gland into its two chief portions the anterior and posterior 

 lobes and determined that, while an extract of the former 

 is devoid of physiological activity when injected into a vein, 

 that of the latter produces the effects upon the blood-pressure. 

 Howell further found the rise of blood-pressure to be accom- 

 panied by a slowing of the action of the heart, and that both 

 the raised blood-pressure and slow cardiac rhythm might be 

 maintained for a considerable time ; and that if a second dose 

 be administered intravenously within a certain time which 

 varies from half an hour to an hour or more after the first 

 dose, these effects are not repeated in other words, a certain 

 immunity is established, which only slowly passes off. 



Cyon has noticed, as did Howell, that the rise of blood-pres- 

 sure is accompanied by slowing of the pulse. Both these effects 

 he attributes to stimulation of the pituitary body by the extract 

 which has been injected. He states that stimulation of the 

 hypophysis in the body, either electrically or mechanically, 

 will produce similar results through the vagi, and that after 

 extirpation of the organ the effects can no longer be produced 

 by injections. 



There is slowing of the isolated mammalian heart, if extract 

 of the "posterior lobe " be perfused through it. 



Schafer and Vincent, working with cats, found that pituitary 

 extract, on administration of a second or third dose, always 

 produces a fall, and not a rise, of pressure (see Fig. 97). 

 The depressor substance was subsequently shown, by the 

 present writer and collaborators, to be common to extracts of 

 all organs and tissues. 



Osborne and Vincent, working with dogs, found, with Howell, 

 a preliminary fall before the rise, but, in most cases, a rise as 

 well as a fall on a subsequent injection. This is what I have 

 observed in a recent series of experiments. 1 



The main facts have been found to hold good as well for 

 extracts made from the human pituitary. 



According to Schafer and Vincent, the cardiac slowing is 



1 In one experiment, even the first administration of pituitary extract 

 produced no Cise, and this result seems to have been due to the previous 

 administration of adrenin. 



