「Fluids flowing from decapitated head into bowl or netting on tray」as STEALING someone else's meat: perhaps the punishment when caught? fundamentally referring to head decapitation of any sort or cause, having one's meat hacked, PINCHED, PILFERED, FILCHED.「Pilfer」means surreptitiously snatching booty.「Stealing」means taking something from another person without the right or permission to do so, epitomized by biting or hacking off a penis, possibly the penalty for STEALING time and pleasure with one of the lord's concubines.
「The whole point of legalism as it, from time to time, dominated Chinese law, was cruel and unusual punishment. As Li Si wrote 2,200 years ago: 'Only an intelligent ruler is capable of applying heavy punishments to light offenses. If light offenses carry heavy punishments, one can imagine what will be done against a serious offense. Thus, the people will not dare to break the laws.'」
[ https://prezi.com/ju1nonzljpiu/the-beginning-of-legalism/ 2023-05-17 ]
Some scholars explain in China, hawking up a large wad of sticky phlegm and then expectorating into a bowl together with a group of buddies was a token of a「vow among thieves」otherwise known today as 'virtual kinship.' Given the risk of transferring blood-borne diseases, probably this action was preferred over becoming a 'blood brother' that was rumored to be common among western hemisphere indigenous folks, yet it served a similar intent without being significantly more hygienic. It seems no mention is made anywhere of what happened later to the contents of that bowl, however, it can be imagined each thief would be required to do something repugnant, perhaps unforgettable (the purpose of this ritual), in order to prove loyalty to the gang, which also might be a bit unsanitary and aid in the transmission of diseases orally. In theory, anyone can just spit into the bowl, but who could drink from it and then later dishonor his fellow thieves, right? (…a thief could). While this explanation may or may not be true, it certainly is possible as a hazing-initiation ritual.

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: to steal; to rob; to plunder; thief; bandit; robber
Japanese EDRDG: thief, to steal
Unihan extended: rob, steal; thief, bandit