Slave: ‘To secure your freedom, tread on poo...!’ Eh??

The answer lies in what Alfredo López Austin refers to as the interconnections between ‘concepts about the human body and social stratification’. Before exploring this, we need to place the Aztec approach to ‘slavery’ in some kind of wider context. Scholars agree that, in the words of Jacques Soustelle, ‘Mexican servitude was quite unlike the accepted notion of slavery’.
López Austin defines a Mexica tlacotli (plural tlatlacotin) as ‘an individual obliged to serve others by virtue of a contract or a penalty imposed on him by law... Being a tlacotli was usually temporary, since the legal relationship could end with payment of the debt that had caused the subjection. In this sense tlatlacoliztli - the situation of the tlacotli - could be compared to a condition of personal pledge, in which the debtor guaranteed with his own person the payment of a debt and in the meanwhile worked for his creditor.’ Some scholars label this a form of ‘contractual indentured servitude’.

Pic 1: Family of collared Aztec slaves; Florentine Codex Book 7

The images of slaves in the codices overwhelmingly show the ‘collared’ variety, presumably as this was the simplest visual representation of general slave status; but we know that in real life ‘ordinary’ slaves were graded, and in the carrying out of their daily tasks they did not wear a heavy wooden collar (quauhcozcatl) with its metre-long wooden rod - these were, after all, designed to mark them out and punish them publicly, to hinder their escape, and to permit chaining several slaves together.
Day to day they were relatively safe from hardship of any kind BUT they ran the serious risk of being demoted to ‘collared slave’ status. This could result from persistent attempts to escape, laziness, disobedience or incompetence, and the slave had to be formally admonished three times in front of witnesses by his/her owner. ‘The penalty was imposed by a judicial sentence that allowed creditors to transfer their ownership without consulting the persons sentenced and could have them destined to a sacrificial death’ (López Austin).
If he did not improve, in Soustelle’s words ‘his master had the right to put a heavy wooden collar on his neck and lead him to the market to be sold’ (see main picture, above).

Pic 3: Collared slaves: the wife and son of a condemned provincial ruler (see pic 2 for details)

To return now to our initial question, López Austin has shown that, in contrast to an Aztec noble, a slave ‘had suffered a physical diminution that explained, at least partially, his degree of subjugation... the parts harmed in the ordinary tlacotli were the tonalli and the teyolia’ (learn more about these in the link below). His heart was physically different to others’, ‘hot’ rather than ‘cold’. What’s more, ‘it may be supposed that contact with human waste supplemented something lacking in the lower part of the tlacotli’s body. [Significantly, the very word tlacotli means ‘The damaged one’]. The fact is that once contact was made, only cleanliness was lacking for him to recover his condition as a free man... The damages to the collared tlatlacotin were repaired when they stepped on excrement; their impurities were cleansed with the purification baths’ (emphasis added).

Pic 5: The array of a slain slave, Florentine Codex Book IX