The brief elaboration of a tube

Once upon a time I was a proper scientist. The sort that did developed hypotheses, or went along with someone else's, and then did experiments to see if they worked. Of course, if you're an astrophysicist you can't build a star and then see if it does what you expect it and so, rather than conducting the experiment yourself, you're obliged to look at the evidence of experiments that nature has carried out on your behalf as it were. But it turned out that I wasn't single minded enough, or prepared to work hard enough, to maintain focus on any one aspect of nature for long enough to actually pursue a career in science and instead drifted off into education. 

Along the way, however, I bumbled from physics into biology and the last of my few published works  was a strange experiment that involved poking electrodes into mouse eggs and then seeing what happened when they were fertilised. Put aside the way in which we got hold of the eggs, or even the sperm, the experiment was primarily interesting because it produced a null result. The thing that we'd hoped would happen simply didn't. If it had, then I suspect that we'd have got the work done much more quickly. It's hard showing that something hasn't happened because it doesn't happen rather than because you've inadvertently done something that stops it happening. In this case, all we could do was show that the subsequent development of the fertilised egg was as near normal as you might expect it to be in the circumstances and support this with a new hypothesis which suggested that the thing we'd hoped would happen wasn't necessary after all.

Now when an animal, any animal's, egg is fertilised the first thing it starts to do is to divide. 2 cells, 4 cells, 8 cells etc. and these cells then begin to arrange themselves into a ball, a blastula. In these experiments this was as far as the ill fated mouse embryos got but, had they been able to continue then they would have begun to undergo what's known as gastrulation. This is when the cells begin to separate into the three layers that will give rise to different sorts of tissues. In particular, this is when the cells which will line your insides become distinguished from those which will be on the outside and those that will lie in between. Insiders give rise to the lining of the gut and other internal organs, outsiders to the skin brain and nervous system and those in the middle to muscle, bone and the circulatory system. 

Now what I find remarkable about early embryos is how alike they all are. There may be differences in scale, but a human embryo looks much like a frog embryo looks much like a chicken embryo looks much like a fly embryo. Now that we know that all life on Earth has a common origin and that the only differences between us are in the details of the code that ends up controlling our ultimate development, its obvious that what works for one early embryo is likely to work for them all with major differences only coming along later in the process. 

During the next phase of development these no differentiated cells begin to migrate and start to form the structures of the adult body. In particular, they begin to form a tube with the inside cells (endoderm) on the inside, the outside cells (ectoderm) on the outside with the middle cells (mesoderm) in between. This tube, the topological equivalent of the hole in a doughnut, will end  up as your guts.

What made me start thinking about all this? Well as usual I was out walking the dog but this time I was wired for sound and found myself listening to "Going Home" by Leonard Cohen. In this song he's singing about his corporeal self from the perspective of his "real/spiritual" self. 

Now in my very first post I questioned the idea that there's a you that's separate from the body that you inhabit, but I have to admit that it often feels as though there is. However, what really hit me in the song was this line "He will speak these words of wisdom like a sage a man of vision though he knows he's really nothing but the brief elaboration of a tube"

Thanks for the context Leonard.