Beauty tip: Apply the moisturizer along Langer’s lines on your face.

This sequence of thoughts was triggered by an observation by Prof. Peter Lee during a biomechanics class.

Many students of biology or anatomy would know that our skin’s dermis (inner layer) is a connective tissue whose largest constituent is collagen. Collagen is a type of extra-cellular protein that looks like three ropes wound around each other at microscopic level. Two interesting facts about skin and collagen are in order: 1) Skin is the largest connective tissue and the largest organ of our body. 2) Collagen is the second most (after meat) animal produce consumed by human beings (if you exclude milk). All of the gelatin used in in food, pharmaceutical, photography, and cosmetic industry comes from animal connective tissues.

During the class, we came to know that the strings of collagen permanently orient themselves along specific directions. This orientation of collagen produces cleavage lines on the surface of skin, and that is what gives rise to all lines seen on our skin. These lines are the cause of wrinkles at elder age. In fact, only few parts of our body do not have clearly defined cleavages and our skin is *stretched* all the time along these lines.

These lines (sort of field lines of a very complex electric or magnetic field) were first mapped out by an Austrian anatomist Carl Langer (1819-1887). He systematically made fine cuts on the cadaver skin and observed in which direction the cuts elongate. The direction of elongation reveals the direction in which the skin is stretched and hence the orientation of underlying collagen. These lines of tension on skin are named after him as Langer’s lines.

Here is what these lines look like..

If you experience a cut along the Langer’s lines, the scar will not be very visible and the wound will heal fast. But if the cut is perpendicular to the Langer’s lines, the wound will tend to open up and the scar will be more visible. Surgeon’s (especially those involved in plastic surgery and beauty services) must respect these lines when making incisions on patient’s skin.

And perhaps these lines are the reason (as Prof. Lee remarked) wives ask their husbands to rub moisturizer on their face not randomly but along certain directions

Any comments from ladies? Do you think the lines in the image above are preferred directions for rubbing creams?

Is it fine to use automated tools to develop software for life-support machine?

The software design technology is assumed to have reached extremely mature state.
Very complex software design tasks such as developing a flight-controller for autonomous scramjet roaring at mach-10 seem to be achievable automatically(Have a look at this story on MATLAB website.)

In such scenario, we assume that software tools available to us are perfect enough to be employed in critical applications such as design of software for life-support machine.
No doubt there are unsolved problems (especially posed by artificial intelligence and information extraction), but we all assume that absolutely essential algorithms (like sorting, searching, reading or writing a file etc. ) used in any program have been perfected.

If you think so, you should look at this post written by Joshua Bloch (one of the developers of JDK.)

Joshua points out how a simple code for finding out a mid-index of an array turns out to be buggy after 20 years of it being written first.

This post clearly points to the need for any software developer to be humble about the quality of his algorithm. The bug-free algorithm works all the time and in all situations. We must admit that we are unlikely to forsee all the situations to which our algorithms may be subjected, so we can never quite get a bug-free algorithm – no matter how simple a thing it does. So we must be very vigilant about bugs – especially in basic algorithms because their cumulative effect is pervasive and huge.

Again, is it fine to use automated tools to develop software for life-support machine?