RELATION SUPRARENAL GLANDS TO CIRCULATION 207 



made in 25 different dogs. In 17, no other effect than contraction was 

 seen at any stage of the experiment or with any dosage. One showed only 

 expansion of the limb, while 7 showed sometimes one and sometimes the 

 other effect, depending upon the dosage or a change in the condition of 

 the animal during the course of the experiment. 



The next step was to determine whether, and if so, to what extent, 

 the limb contraction was due to vasoconstriction in the muscle. The com- 

 ponents of the limb to be considered are the bone, muscle, and skin. Since 

 the volume of the bone is fixed, the contraction must have been due to vaso- 

 constriction in either the muscle or the skin. To determine the relative 

 parts played by each, the volume change was first determined in the intact 

 limb and then after removal of the skin. The result of removing the 

 skin was striking. Under nearly all conditions of dosage, duration of ad- 

 ministration, and resultant effects upon blood-pressure, epinephrin caused 

 expansion of the skinned leg. If, however, very large doses were used 

 contraction ordinarily occurred (Gunning). The experiment was varied 

 by recording simultaneously the volume changes in two legs, one being 

 skinned and the other intact. The former dilated while the latter ordi- 

 narily contracted. From such observations it follows that the total effect 

 in the limb is a composite made up of dilatation in the muscle and con- 

 striction in the skin. 



This deduction was put to direct test. Capps and Matthews (1913) 

 had showed that epinephrin injections of the magnitude used in these 

 experiments have little or no effect upon venous blood-pressure. Measur- 

 ing the rate of outflow from an open vein, therefore, under various con- 

 ditions of epinephrin administration should afford a reliable index of the 

 effects of such administration upon the blood flow in an intact animal. 

 A femoral vein was exposed in the groin. One of its branches coming 

 from an underlying muscle was further isolated and cannulated. Similar- 

 ly, a cutaneous branch of the same femoral vein was cannulated. The 

 venous outflow was then recorded by means of a drop marker. Epinephrin 

 was administered intravenously, either by instantaneous injections or by 

 infusions at various rates. The rate of venous outflow from the muscle 

 was increased, while that from the skin was decreased. The experi- 

 ments were repeated many times. The effects in both cases were proved 

 to be active because they occurred independently of increase or decrease in 

 systemic blood-pressure. 



The foregoing observations were subsequently confirmed by Hartman 

 and Eraser and by Gruber (c) . Gruber reported the additional observation 

 that cutting the nerves to a muscle prevents vasodilatation in the dener- 

 vated region during the early period in which local vasomotor tonus is 

 abolished. Subsequently, however, as vasomotor tonus is regained it was 

 found that epinephrin vasodilatation can again be evoked (Fi^. 7). 



