106 



N. E. Shaw 



stimulation stopped. Muscle relaxation was accompanied by a further increase in 

 muscle blood-flow which returned to its resting level after about three minutes. There 

 was an initial fall in medullary pressure and blood flow followed by a rise until 

 nerve stimulation ceased when there was a sudden fall followed by a marked rise in 

 both these characteristics of the circulation in bone (Fig. 1). 



B.P. 



M. P. 



lO- 

 MMHG 

 BONE 



MUSCLE 



J30SECSL 



:OND 

 PERIPHERAL FEMORAL NERVE 



Fig. 1. Upper tracings — Arterial blood-pressure and intramedullary pressure. Lower tracings — Bone blood- 

 flow and muscle blood-flow. The muscle blood-flow falls initially but rises above its resting level during con- 

 tinued stimulation and reactive hyperaemia causes a further increase when nerve stimulation stops. The imme- 

 diate fall in medullary pressure and bone blood-tlow are apparent and the fall and subsequent rise when nerve 

 stimulation is withdrawn is shown 



B. P. 



M.P. 



I20 



90- 



ii^»^li^<>ii Wim I ii i i 'n i iwPi i <M* M «>w > M i » ai>i#WiNNt>i 



30 

 MM.HG 



¥\^ 





BONE 



MUSCLE 



4 VOLTS 3 SEC INTERVAL 

 PERIPHERAL FEMORAL NERVE 



Fig. 2. Upper tracings — Arterial blood-pressure and intramedullary pressure in the femur. Lower tracings — . 



Bone blood-flow and muscle blood-flow. There is a gradual rise in muscle blood-flow with repeated nerve 



stimulation; sudden rises in bone blood-flow and intramedullary pressure occur with each muscle contraction, 



but the intramedullary pressure gradually fails 



(2) Repeated nerve stimulation caused intermittent muscle contractions each 

 temporarily reducing the muscle blood-flow, which however, increased progressively 

 during muscle relaxation. This change was associated with a momentary rise in the 

 intramedullary pressure and the blood flow in bone during each muscle contraction, 

 but there was a gradual fall in medullary pressure after each stimulus (Fig. 2). 



