Chapter 8

Democritus of Abdera and certain others who have treated of respiration¹, while saying nothing definite about the lungless animals, nevertheless seem to speak as if all breathed. But Anaxagoras and Diogenes both maintain that all breathe, and state the manner in which fishes and oysters² respire. Anaxagoras says that when fishes discharge water through their gills, air is formed in the mouth, for there can be no vacuum, and that it is by drawing in this that they respire. Diogenes’ statement is that, when they discharge water through their gills, they suck the air out of the water surrounding the mouth by means of the vacuum formed in the mouth, for he believes there is air in the water.

But these theories are untenable. Firstly, they state only what is the common element in both operations and so leave out the half of the matter. For what goes by the name of respiration consists, on the one hand, of inhalation, and, on the other, of the exhalation of breath; but, about the latter they say nothing, nor do they describe how such animals emit their breath. Indeed, explanation is for them impossible for, when the creatures respire, they must discharge their breath by the same passage as that by which they draw it in, and this must happen in alternation. Hence, as a result, they must take the water into their mouth at the same time as they breathe out. But the air and the water must meet and obstruct³ each other. Further, when they discharge the water they must emit their breath by the mouth or the gills, and the result will be that they will breathe in and breathe out at the same time, for it is at that moment that respiration is said to occur. But it is impossible that they should do both at the same time. Hence, if respiring creatures must both exhale⁴ and inhale⁵ the air, and if none of these animals can breathe out, evidently none can respire at all.

1 respiration   

n.呼吸作用；一次呼吸；植物光合作用

参考例句：

• They tried artificial respiration but it was of no avail.他们试做人工呼吸，可是无效。
• They made frequent checks on his respiration,pulse and blood.他们经常检查他的呼吸、脉搏和血液。

2 oysters   

牡蛎( oyster的名词复数 )

参考例句：

• We don't have oysters tonight, but the crayfish are very good. 我们今晚没有牡蛎供应。但小龙虾是非常好。
• She carried a piping hot grill of oysters and bacon. 她端出一盘滚烫的烤牡蛎和咸肉。

3 obstruct   

v.阻隔，阻塞(道路、通道等)；n.阻碍物，障碍物

参考例句：

• He became still more dissatisfied with it and secretly did everything in his power to obstruct it.他对此更不满意，尽在暗里使绊子。
• The fallen trees obstruct the road.倒下的树将路堵住了。

4 exhale   

v.呼气，散出，吐出，蒸发

参考例句：

• Sweet odours exhale from flowers.花儿散发出花香。
• Wade exhaled a cloud of smoke and coughed.韦德吐出一口烟，然后咳嗽起来。

5 inhale   

v.吸入(气体等)，吸(烟)

参考例句：

• Don't inhale dust into your lung.别把灰尘吸进肺里。
• They are pleased to not inhale second hand smoke.他们很高兴他们再也不会吸到二手烟了。