Something else you won’t read in standard textbooks or hear in those lectures where politeness is deemed more important than understanding concerns what happens to the anus immediately following defecation. Again, this information was provided by one of my old professors* (the one mentioned in a previous post on a similar topic).
It transpires that the process of defaecation is not completely over once the faeces have left the body. The muscles around the anus, having opened, proceed to close but remain active for a brief period of time. (I’m afraid that I don’t know exactly how long this lasts, but it would appear to be for only a matter of minutes.)
As described by my old professor, these muscles tend to ‘writhe.’ That is, they move in a twisting, even worm-like fashion. This may simply be a way of their repositioning themselves back into a stable (comfortable?) arrangement until defecation takes place again. This writhing may have the effect of helping to clear the anal canal of any remaining faeces and should (Prof. advocated) be allowed sufficient time to complete the process.
Although this may not happen every time, allowing a period of relaxation after the main act of defecation sometimes results in small bits of faeces falling from the anus after a few minutes without any extra effort.
* NB All of my ‘old’ professors are now ‘late’ professors. I’ve read the obituaries. I hope, though, that in reporting what I can remember them saying, something survives.
