The basis for Walter Shandy’s Ass – from St. Jerome’s Life of Hilarion (5th paragraph):
[Satan] therefore tickled his senses and, as is his wont, lighted in his maturing body the fires of lust. This mere beginner in Christ’s school was forced to think of what he knew not, and to revolve whole trains of thought concerning that of which he had no experience. Angry with himself and beating his bosom (as if with the blow of his hand he could shut out his thoughts) “Ass!” he exclaimed, “I’ll stop your kicking, I will not feed you with barley, but with chaff. I will weaken you with hunger and thirst, I will lade you with heavy burdens, I will drive you through heat and cold, that you may think more of food than wantonness.”
Titillabat itaque sensus eius, et pubescenti corpori solita voluptatum incendia suggerebat. Cogebatur tirunculus Christi cogitare quod nesciebat, et eius rei animo pompam volvere, cuius experimenta non noverat. Iratus itaque sibi, et pectus pugnis verberans (quasi cogitationes caede manus posset excludere): Ergo, inquit, aselle, faciam, ut non calcitres: nec te hordeo alam, sed paleis. Fame te conficiam et siti: gravi onerabo pendere, per aestus indagabo et frigora, ut cibum potius quam lasciviam cogites.