520 



Messrs. M. Flack, L. Hill, and J. McQueen. 



the artery and vein alone, excluding the tissue schema, or through the 

 artery alone. 



For the tissue schema we have substituted a human kidney in some of 

 our experiments. We finally modified the above schema and made a still 

 closer imitation of the conditions which pertain to the circulation in the 

 arm. The artery passes through the tissue schema and is surrounded by 

 it. The inflow tube branches and the water flows through both the tissue 

 schema and the artery ; the outflow tubes from artery and tissue schema 

 join and pass to another length of artery placed in the same compression 

 chamber ; this acts as the vein. 



We have used two such complete schemata joined in series in some of 

 our experiments, one representing the upper arm, the other the forearm 

 (%• 2). 



Experiment I. 



We first observed the effect of circulating water through two lengths of 

 artery — in place of one — both being placed in the same compression 

 chamber. The water flowed through (1) the first length of artery, (2) a 

 connecting length of rubber tubing, (3) the second length of artery, and so 

 to the outlet (fig. 3). 



When the compression chamber was connected with the recording spring 



TO PRESSURE BOTTLE 



Fig. 3. 



manometer the record showed that the maximal pulsation occurred at a 

 lower level when the flow was through two lengths of artery (fig. 4) than 

 when it was through one length (fig. 5). 



Owing to the frictional resistance in the length of tube through which the 

 water flowed, the systolic pressure was partly spent in distending the labile 

 first length of artery and in overcoming the frictional resistance during 

 diastole ; the second piece of artery, in consequence, had the lower diastolic 



