“Little valve to let the blood out; ’nother little valve to let it in—just like an internal combustion engine, which it is?”
“Of course.”
“And s’posin’ that stops?”
“You die.”
“Yes. Now, look here. S’posin’ you take a good big hypodermic, empty, and dig it into one of the big arteries and push the handle—what would happen? What would happen, doctor? You’d be pumpin’ a big air-bubble into your engine feed, wouldn’t you? What would become of your circulation, then?”
“It would stop it,” said the doctor, without hesitation. “That is why nurses have to be particular to fill the syringe properly, especially when doing an intra-venous injection.”
“I knew it was the kind of thing you learnt in the fourth form. Well, go on. Your circulation would stop—it would be like an embolism in its effect, wouldn’t it?”
“Only if it was in a main artery, of course. In a small vein the blood would find a way round. That is why” (this seemed to be the doctor’s favourite opening) “that is why it is so important that embolisms—blood-clots—should be dispersed as soon as possible and not left to wander about the system.”
“Yes—yes—but the air-bubble, doctor—in a main artery—say the femoral or the big vein in the bend of the elbow—that would stop the circulation, wouldn’t it? How soon?”
“Why, at once. The heart would stop beating.”