The Compendium of Caraka 8.11.21

8.11.21

aratnimaṣṭādaśaṣoḍaśāṅgulaṃ tathaiva netraṃ hi &daśāṅgulaṃ kramāt/
gajoṣṭragośvāvyajabastisaṃdhau caturthabhāgopanayaṃ hitaṃ vadet&//

The pipe should be one aratni, eighteen fingers, sixteen fingers, / and ten fingers [long] respectively; at the junction of the pipe and the enema bag for elephants, camels, cattle, horses, sheep, and goats, applying a fourth part is stated to be beneficial.