Visuddhimagga VIII-165

Yā pana tesaṃ dīgharassatā, sā addhānavasena veditabbā.

其次当知那（出入息的）长短是依时间的。

Ñ(VIII,165): But their length and shortness should be understood by extent (addhāna).

Yathā hi okāsaddhānaṃ pharitvā ṭhitaṃ udakaṃ vā vālikā vā ‘‘dīghamudakaṃ dīghā vālikā, rassamudakaṃ rassā vālikā’’ti vuccati,

譬如展于空间的水或沙，而说长水长沙，或短水短沙，

Ñ: For just as water or sand that occupies an extent of space is called a 'long water', a 'long sand', a 'short water', a 'short sand',

evaṃ cuṇṇavicuṇṇāpi assāsapassāsā hatthisarīre ca ahisarīre ca tesaṃ attabhāvasaṅkhātaṃ dīghaṃ addhānaṃ saṇikaṃ pūretvā saṇikameva nikkhamanti.

如是一片片的出入息，在象与蛇的身中，徐徐地充满他们长度的肉体，又徐徐出去，

Ñ: so in the case of elephants' and snakes' bodies the in-breaths and out-breaths regarded as particles slowly fill the long extent, in other words, their persons, and slowly go out again.

Tasmā dīghāti vuccanti.

所以说长（的出入息）；

Ñ: That is why they are called 'long'.

Sunakhasasādīnaṃ attabhāvasaṅkhātaṃ rassaṃ addhānaṃ sīghaṃ pūretvā sīghameva nikkhamanti,

急速地充满犬兔等的短度的肉体，又速速地出去，

Ñ: They rapidly fill a short extent, in other words, the person of a dog, a hare, etc., and rapidly go out again.

tasmā rassāti vuccanti.

所以说短（的出入息）。

Ñ: That is why they are called 'short'.