Chapter 21

The explanation of the admission of air and respiration¹ in those animals in which a lung is found, and especially in those in which it is full of blood, is to be found in the fact that it is of a spongy nature and full of tubes, and that it is the most fully² charged with blood of all the visceral organs. All animals with a full-blooded lung require rapid refrigeration because there is little scope for deviation³ from the normal amount of their vital fire; the air also must penetrate⁴ all through it on account of the large quantity of blood and heat it contains. But both these operations can be easily performed by air, for, being of a subtle nature, it penetrates⁵ everywhere and that rapidly, and so performs its cooling function; but water has the opposite characteristics.

The reason why animals with a full-blooded lung respire most is hence manifest; the more heat there is, the greater is the need for refrigeration, and at the same time breath can easily pass to the source of heat in the heart.

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 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

3 deviation   

n.背离，偏离；偏差，偏向；离题

参考例句：

• Deviation from this rule are very rare.很少有违反这条规则的。
• Any deviation from the party's faith is seen as betrayal.任何对党的信仰的偏离被视作背叛。

4 penetrate   

v.透(渗)入；刺入，刺穿；洞察，了解

参考例句：

• Western ideas penetrate slowly through the East.西方观念逐渐传入东方。
• The sunshine could not penetrate where the trees were thickest.阳光不能透入树木最浓密的地方。

5 penetrates   

v.穿过( penetrate的第三人称单数 )；刺入；了解；渗透

参考例句：

• This is a telescope that penetrates to the remote parts of the universe. 这是一架能看到宇宙中遥远地方的望远镜。 来自《简明英汉词典》
• The dust is so fine that it easily penetrates all the buildings. 尘土极细，能极轻易地钻入一切建筑物。 来自辞典例句