HYPOPHYSIS CEREBRI 325 



lar portion of the hypophysis into dogs and rabbits, and produced 

 a profound fall in blood-pressure which, in atrophied animals, lasts 

 for a comparatively long time. The lowered pressure, which, at the 

 end of forty seconds, spontaneously returns to the normal figure, 

 may be relieved by means of adrenalin. In two instances, after 

 injection of the extract, the blood-pressure fell to zero, and 

 respiratory and cardiac activity ceased. In one case the animal 

 was saved by the injection of 2 c.cm. pituitrinum infundibulare ; 

 the heart-beats recommenced, the blood-pressure rose rapidly to 

 normal, and the animal completely recovered. 



Finally, L. Etienne and Parisot found that the repeated injec- 

 tion of pituitary extract into rabbits produced permanent hyper- 

 tension and cardiac hypertrophy, which were apparent fifteen days 

 after the last injection ; there were, however, no sclerotic changes 

 in the vessels. 



The results which have been described comprise the whole of 

 the material at present available concerning the influence of 

 pituitary extract upon the circulation. It may then be taken as 

 proven that pituitary extract, or rather the extract of the posterior 

 hypophyseal lobe, produces a 'high degree of blood-pressure, which 

 differs from that provoked by adrenalin in its slighter intensity 

 and longer duration. The diminished, or negative, action of a 

 second injection may be regarded as specific. 



The hypotensive action of pituitary extract described by cer- 

 tain authors demands further investigation. It is very necessary 

 that we should know whether the fall in pressure is a by-effect of 

 pituitary extract, or whether it is due to a specific activity on the 

 part of the glandular portion of the organ. 



There is no doubt that the rise in arterial tension is mainly 

 the result of peripheral vaso-contraction. But further investiga- 

 tion is necessary both to locate the seat of this vaso-contraction 

 and to decide whether the vaso-contraction which takes place in 

 the thyroid gland and the nasal mucous membranes, and the 

 vaso-dilation which takes place in the kidney, are specific effects 

 of pituitary extract. 



Pituitary extract also influences the action of the heart, by 

 slowing and strengthening its beats. This effect is in part 

 attributable to stimulation of the cardiac inhibitory nervous 

 centres. The experiments of Hedboom and Allen, Cleghorn, 

 and, later, Herring, with the living heart from frogs and mammals, 

 have proved, however, that the slowing of the pulse is unaffected 

 by resection of the vagi, and it seems probable from this that 

 pituitary extract also exercises a direct action upon the muscular 

 substance of the heart. This conclusion is further justified by 

 the fact that the constriction of the vessels is produced not, as in 

 the case of adrenalin, by stimulation of the peripheral nerve- 

 terminals, but by a direct action upon the involuntary muscles ; 

 moreover, the effect which pituitary extract has upon the muscles 

 is also demonstrable in the case of other organs. 



