Tally the bone yard

It's that time of year when the 1st Year Sporty People try to work out how many bones they have about their person.  I've done this before in 2014 and 2015 and it's an exercise that keeps on giving. One of the pervasive anti-science elements of teaching practice is to say or imply that there is a correct answer.  If we know the answer already then we're not doing science. I've heard all the arguments about giving students tasks to do which improve their dexterity and practice at the bench so that they become, eventually, a good pair of hands. For example, talking to my Yr 3 Microbiologists on Thursday, I told them that the 60 hours of lab time we have together is An Opportunity . . . to learn their craft through repeated practice.  It wasn't about the results, which are quite unlikely to be either new or unexpected. It was about doing Gram stains until you no longer have to follow the protocol from a book but have internalised it. It was about pouring Petri dishes in a zen like state so that each is the same thickness and in a neat stack. It's about using the autoclave so often that you never forget to label the media bottles; you know the task list so well you dream about it; you know the tricks for expediting the process to win a tea-break in the middle of the afternoon.

Mais, revenons nous a nos squelettes! This year, each group of 2 or 3 people was tasked to inventory a typical skeleton so that it came to N=206. We all agreed that 206 was the Correct Answer. But it transpired that nobody had the same idea about where these 206 bones were located. I put a blank table up on the board and invited the 6 different teams to enter their numbers.  This was a little more constraining than perhaps fair because the rules of engagement didn't, for example, require that the foot and leg should be treated separately. The headings also didn't clarify where the pelvis, clavicle and scapular should be binned.

Group	1	2	3	4	5	6
Skull	14	11	14	24	31	22
Vertebrae	33	33	33	25	33	33
Ribs	25	25	25	25	27	25
Legs	16	15	18	10	16	10
Arms	12	10	10	10	10	10
Hands	54	54	54	54	54	54
Feet	52	56	52	48	42	53
Total	206	204	206	196	212	206

What's striking, and depressing, about these data is that half the class got the correct answer but achieved this is different ways. Group six didn't even both to make sure that tally in each of the 7 category bins [=207] summed to the 206 Total! I think, formally, they'd be guilt of plagiarism because the numbers - of bones in the skull for starters - are suspiciously close to correct.  But there are 7 extra bones rattling around inside the skull but not attached to it: 2 each of incus malleus and stapes in the ears and one hyoid in the neck. 206land counts two bones in the pelvis L & R innominate rather than 6: two each of ileum, ischium & pubis.
So here is the list, it's normal /definitive, and 206 is just plain wrong:
Axial = 87 (8+14+7+33+25)

• Cranium N=8: occipital bone, 2 temporal bones, 2 parietal bones, sphenoid bone, ethmoid bone, frontal bone
• Face N=14: vomer, 2 conchae, 2 nasal bones, 2 maxilla, mandible, 2 palatine bones, 2 zygomatic bones, 2 lacrimal bones
• Extras N=7: hyoid, ears: 2 stapes, 2 malleus, 2 incus
• Vertebrae N=33, 7 cervical,12 thoracic, 5 lumbar, 5 sacral, 4 coccyx
• Ribs+sternum N=25

Appendicular = 126 (10+10+54+52)

• Shoulder and arms N=10: 2 each scapula, clavicle, humerus, ulna, radius
• Pelvis and legs N=10: 2 each innominate, femur, patella, femur, tibia
• Hands N=54: 16 carpals, 38 metacarpals and phalanges (thumb only 2 phalanges)
• Feet N=52: 14 tarsals, 38 metacarpals and phalanges (great toe ditto)

"206" must be ignoring the ear-bone's connected to the ear-bone.And the whole exercise is ignoring the polymorphism, and sesamoid bones and riding rough-shod over issues of definition which I elaborated upon this time last year.