Playing Detectives

(A bit of fun but a learning experience too!) by Maurice Smith. Aug. 1997



What isn't about Microscopy?

I recently had my leg pulled over one of our front page animation's. The one concerned was of two crickets (or are they locusts?) running along piggy-backed as they embarked on their favourite past-time of making more crickets. "It made me laugh...", said my friendly tormentor: "...but what has it to do with microscopy?"

This is the not the first time such a question has been asked of the crew here at Micscape and Microscopy-UK. The problem here lies with different perceptions about what Amateur Microscopy means. Is it for example about studying life and processes only at the microscopical scale, or is it about studying life in general along with its processes - and using microscopy as one tool of many to help reveal greater truth and insight?!

I believe everything there is - man, beast, cosmos, nature...  you name it, I'll include it too - is built upon the foundation of microscopical processes. So this month, I thought I'd demonstrate to you just one such connection between the everyday world and a process in the microscopical one. We are going to play a little game together: a game where we become Amateur Microscopy Detectives!
 

A Question...

What is the connection between the diagram below and a criminal act?
   
Okay, I guess it's not a very good diagram but we will take a look at a better one later. Maybe, you'll get to see the connection between biology, microscopy, and criminal acts if I hold up a bit of my anatomy for you to see.... NO... not that! This is a family site! Here's the bit I meant...

YUP! It's my finger tip, or more precisely - the fine epidermal ridges which comprise what is commonly called : a finger-print! You start to see the connection now with crime, I bet. We all have a unique pattern of lines like this on our finger tips. Normally, they fall into three categories: arch, loop, and whorls, although variations between loops and whorls can exist. I'm not an expert but I think my one is a double-whorl. Their names are self explanatory but you may need to look very carefully to distinguish between loops and whorls.

In the UK, loops are commonest (70% of the population), whorls are next (25%), and arches are the rarest at 5% of the population. Take a look at your one now - what type is it?

Not easy to see, eh..? Well get out your trusty 8x magnifier and take a look:-
 

Most people know that many crimes have been solved though the use of a technique called 'finger-printing'. When someone commits a crime, especially where it wasn't planned, they will inevitably have touched something at the crime scene. In doing so, they will have left behind an invisible mark which can be proven to have belonged to only one human-being on the planet. Special people visit a crime scene with the police. By dusting objects with a fine powder, they are able to reveal  finger-prints  left behind....

... like my one here!

There's no magic involved. The chalk dust that I used to get this print works just the same way as the finer powder used by the people investigating crime-scenes: the dust sticks to the fine lines of sweat which have been deposited on the object from the high points (ridges) of the suspect's skin. Where the lines are dark, no sweat was deposited because it was still trapped in the low points (valleys) of the skin.
 
Can you imagine all the crimes that have been solved simply because  we possess two biological features: patterns on the surface of our skin, and sweat glands!

Now, as it happens, sweat glands in the human skin are quite difficult to spot in specimen slides. Many students and amateur microscopists have to play at being detectives themselves to find them. Here, let me show you a rather bad specimen of a skin section. This one below was borrowed from a school where biology students would have been using it to identify processes like sweat glands along with a lot of other things present in human skin.  

I've marked two areas of interest as A and B which we I will be referring to in a moment, but first of all, let's take a look at a diagram from a typical biology text book and see how it helps (huh... I wonder about some of these books!) us to identify where the glands are what we should be looking for.
 

Here's a very quick and dirty diagram. Text books normally show skin sections more refined than this.

That wormy, wrigley, looking thing is the process we wish to consider in more detail. The problem is that this 3D solid looking section of skin has been put together conceptually through the mind of an artist. In real life, to see a skin section, you have to slice it up so thin that you only get to see bits of the items (processes) buried in the skin. If you are lucky, the section you get in the slide to study might contain a bit of everything. It is rare to get perfect examples of all - or even the majority of things you would wish to study - in a single section!

So how the heck do you identify a sweat gland. Well you have to follow a few clues. First of all - see how the gland starts out to be very entwined at its base and then twists and spirals up to the surface of the skin, like a winding tube getting thinner and thinner?

You do... good! Let me show you a slide where that 'wrigley' bit at the base is present:-

What you actually get to see is a pattern of circles and elongated circles: cross-sections of the sweat gland tube in many places as it loops back and forth, around and around! With a little care, you can even get to see which circles represent sections of duct as distinct from secretory parts of the gland.

The duct itself 'meanders' up to the skin surface. The tube gets thinner, and a section through it yields small circles (or rings) representing the duct wall. Here's another diagram (very quickly done) to demonstrate:-

After looking at this, go back up and examine the image with A and B indicating two processes. I reckon that A is not a duct because even though it 'wanders' up to the surface, it is intact: more likely to be muscle involved with erecting body hair! Item B does look like a trail of tiny circles, maybe a sweat duct, very thin, as it  approaches the skin's surface. But there is not the 'tell-tale' system of clustered circles at the end of the trail... so is it a sweat gland duct or one of many other processes just beneath the surface of the skin? I don't know either!

It's a heat wave here in the UK. A hot and humid night. I have a cooler on in in my room to keep down the heat from computers, lights, cameras, and the extraordinary weather. My body is fighting to evaporate moisture to maintain a constant temperature, as I struggle to make ready this article. If my sweat glands packed up... where would I be?! The humidity is high, the sweat remains like a thin film on my body. I am growing confused... where did I begin this page.... ah... yes: crime, diagrams, and connections!

Go back up to the very first image at the top of the page. Can you see the connection now? If so, you have taken your first step into becoming a Microscopist detective. Welcome to a whole new world!

Maurice Smith - August 1997 - "Sweating like mad!"



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