J.R.Ackerley and Tulip
Dogs read the world through their noses and write their history in urine. Urine is another and highly complex source of social information; it is a language, a code, by means of which they not only express their feelings and emotions but communicate with and appraise each other. Tulip is particularly instructive in this matter when she is in season, for on these occasions she has numerous callers who leave the marks of their attention round the front door. On her way in and out she reads, with her long black nose, these superimposed stains, and the care with which she studies them is so meticulous that she gives the impression of actually identifying her acquaintances and friends.
She has two kinds of urination, Necessity and Social. Different stances are usually, though not invariably, adopted for each. In necessity she squats squarely and abruptly, right down on her shins, her hind legs forming a kind of dam against the stream that gushes out from behind; her tail curves up like a scimitar; her expression is complacent. For social urination, which is mostly preceded by the act of smelling, she seldom squats, but balances herslef on one hind leg, the other being withdrawn or cocked up in the air. The reasons for this seems obvious; she is watering some special thing and wishes to avoid touching it. It may also be that in this attitude she can more accurately bestow her drops. Often they are merely drops, a single token drop will do, for the social flow is less copious. The expression on her face is business-like, as though she were signing a check.
-- from My Dog Tulip by J. R. Ackerley