be made into leather for furniture, accessories, and clothing. Slave hair could be shaved and used for stuffing in pillows and furniture. In some instances, the inner body tissue of slaves (fat, bones, etc) could be made into soap, trophies, and other commodities. Medical experimentation on slaves was also commonplace. Slaves were routinely used as medical specimens forced to take part in experimental surgeries, amputations, disease research, and developing medical techniques. In many cases, slave cadavers were used in demonstrations and dissection tables. Slave codes To help regulate the relationship between slave and owner, including legal support for keeping the slave as property, states established slave codes, most based on laws existing since the colonial era. The code for the District of Columbia defined a slave as "a human being, who is by law deprived of his or her liberty for life, and is the property of another". While each state had its own slave code, many concepts were shared throughout the slave states. According to the slave codes, some of which were passed in reaction to slave rebellions, teaching a slave to read or write was illegal. This prohibition was unique to American slavery, believed to reduce slaves forming aspirations that could lead to escape or rebellion. Informal education occurred when white children taught slave companions what they were learning; in other cases, adult slaves learned from free artisan workers, especially if located in cities, where there was more freedom of movement. In Alabama, slaves were not allowed to leave their master's premises without written consent or passes. This was a common requirement in other states as well, and locally run patrols (known to slaves as pater rollers) often checked the passes of slaves who appeared to be away from their plantations. In Alabama slaves were prohibited from trading goods among themselves. In Virginia, a slave was not permitted to drink in public within one mile of his master or during public gatherings. Slaves were not permitted to carry firearms in any of the slave states. Slaves were generally prohibited by law from associating in groups, with the exception of worship services (a reason why the Black Church is such a notable institution in black communities today). Following Nat Turner's rebellion in 1831, which raised white fears throughout the South, some states also prohibited or restricted religious gatherings of slaves, or required that they be officiated by white men.