NEW YORK – For Hippocrates, health was an equilibrium of the body governed by the four humors, melancholic, phlegmatic, sanguine and choleric. With this in mind, how does Microsoft stand up to psychological cross-examination? The first three humors seem to embody its Chairman Bill Gates, but where does the software leviathan’s spleen reside? In the Hippocratic world, the standardized personality type for a choleric individual is vengeful, short-tempered and ambitious. By one account, this fits Steve Ballmer, Microsoft’s chief executive.

According to documents presented in a legal tussle between Internet rivals Microsoft and Google, Ballmer vowed to “kill” Google in an obscenity-laden tirade last November. Sworn evidence from a former Microsoft engineer, Mark Lucovsky, claimed Ballmer picked up his chair and hurled it across his office, before saying of Google’s CEO Eric Schmidt: “I’m going to bury that guy, I have done it before, and I will do it again. I’m going to kill Google.” And Lucovsky reckons a couple of those verbs were preceded by an obscene gerund.

The evidence has come to light in the legal showdown between the behemoths, triggered by Google’s hiring of a former Microsoft executive, Kai Fu-Lee. Microsoft sued Google, accusing it of poaching Lee to head up a new research lab in China. Google immediately countered the suit, contending that Microsoft’s clause was an illegal restraint of trade since it violated laws in California, where Google is based, giving workers the right to change jobs. But Microsoft prevailed in late July when a judge issued an order temporarily barring Lee from working at Google.

Lucovsky claims he met with Ballmer last November to discuss his decision to leave the company. The CEO allegedly lost his cool after learning that Lucovsky was moving to Google. Ballmer described Lucovsky’s recollection as a “gross exaggeration,” adding that “the characterization of that meeting is not accurate.”