420 DR THOMAS R. FRASER ON STROPHANTHUS HISPID US. 



adequately explain the changes in the heart's action characterising the diastolic type. It 

 is necessary to regard this action as operating simultaneously with the action on muscle 

 that tends to increase its contractility ; the former slowing the rate of contraction, and 

 giving an opportunity for the heart to receive an exceptionally large volume of blood, 

 the latter rendering each contraction a more perfect and complete one than it otherwise 

 could be. In such combination, therefore, as results from the administration of minimum- 

 lethal or of non-lethal or therapeutic doses, the expansion of the heart's chambers is 

 augmented, the systolic contractions are rendered more complete, and the working power 

 of the heart is enhanced. 



B. Blood-Vessels. 



In order to determine if Strophanthus produces any change in the size of blood- 

 vessels by an action on their structures, perfusion experiments were made on frogs 

 with solutions of extract of Strophanthus and of strophanthin in normal saline. The 

 same preparation of each substance was employed in the experiments, so as to avoid any 

 fallacy that might arise from possible variations in these substances. 



For purposes of comparison several experiments were also made with normal (075 

 per cent.) solution of chloride of sodium, and with digitalin — the latter being sometimes 

 used alone, and at other times substituted for solutions of extract of Strophanthus or 

 strophanthin, in experiments in which one or other of these substances had already 

 been allowed to flow through the blood-vessels. The digitalin was an English specimen, 

 entirely and freely soluble in water, and the same digitalin as was also used in some of 

 the experiments on isolated frogs' hearts (footnote, p. 403). 



The perfusion apparatus consisted of three reservoirs, the contents of which were 

 maintained at a nearly constant level by means of Marriotte's flasks. One of the 

 reservoirs contained normal saline, another a solution of extract of Strophanthus or 

 strophanthin in normal saline, and the third a solution of digitalin, also in normal 

 saline. Each reservoir was connected with one of the limbs of a four-limbed canula by 

 an india-rubber tube, to which was attached a binding screw. 



After the brain and medulla oblongata and spinalis of the frog had been destroyed, 

 the vense cavse were divided, and the fourth limb of the canula was inserted into the 

 ductus arteriosus. The binding screw on the tube leading to the reservoir containing 

 normal saline was then opened, and after the blood had been entirely washed out of the 

 blood-vessels, the saline escaping from the vense cavse was collected in a graduated glass, 

 and measured at brief intervals. The normal flow was thus ascertained, and thereafter 

 the tube leading to one or other of the reservoirs containing Strophanthus and digitalin 

 was opened, and the tube leading to the saline reservoir was closed. The flow under the 

 action of Strophanthus or digitalin was thus ascertained. In some of the experiments 

 the contents of the three reservoirs were successively passed through the blood-vessels. 

 It is almost needless to state that increase of flow would imply dilatation of blood-vessels, 

 and reduction of flow contraction. 



