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



65 60 50 40 10 5 cm. H 2 0. 



Artery 

 maximal pulse. 



Fig. 9. 



"Vein 

 maximal pulse. 



On. 



The following were the outflows at each stage : — 



Compression. 



Outflow. 



Compression. 



cm. H 2 0. 

 

 5 

 10 

 40 



60 

 65 



c.c. per min. 

 146 

 71 

 63 

 33 



11 



2 



Vein beginning to deform during each diastole. 

 Maximal pulse of vein. 



Tissue schema shrinking. Manometer scarcely 



pulses at all. 

 Artery beginning to deform during each diastole. 

 Maximal pulsation of artery. 



Experiment V elucidates the behaviour of the brain when compressed. 

 When the brain is compressed by fluid forced into the subdural cavity the 

 capillaries, venules, etc., similarly shrink, the pressure rises in these vessels, 

 and the whole cerebral vascular system approximates to a rigid system and 

 gives a small cerebral pulse. Similarly, when the armlet compresses the 

 arm, part of the blood contained in the tissue vessels is expelled and the 

 remaining patent vessels approximate to a rigid system, in which arterial 

 pressure pertains and through which a diminished flow continues until these 

 are emptied ; the artery itself is then flattened ; that is, when the systolic 

 pressure is overtopped. 



Experiment VI. 



In Experiment VI the flow was arranged through the artery and the tissue 

 schema placed in separate compression chambers. These chambers were 

 connected with each other and the manometer (fig. 1). 



A. On compression the tissue schema first shrank, then the artery began to 

 flatten and the maximal pulse resulted. On decompression the maximal 

 pulse was more ample and occurred at a lower level than on compression 

 (%. 10). 



Like results were obtained when the tissue schema was replaced by the 



