Since you, esteemed reader, seem to be as addicted to words as I am, here is a tip. I have recently subscribed to 'Word of the Day', a free service offered by the Merriam-Webster company which you can reach on the Web either at: www.merriam-webster.com, or by joining the list via e-mail, for which you must send a blank e-mail to: mw-wod-subscribe-request@listserv.webster.m-w.com.

Every day a new word arrives in my mailbox, with accompanying notes that give everything from its definition, usage and etymology. By now you will be familiar with etymologies - that is, word histories. The etymology of 'etymology' is itself quite straightforward: 'etymon' means 'literal meaning of a word according to its origin'. Greek 'etymon' in turn comes from 'etymos', which means true. I have already confused you with my 'etyrminology' chimera and will confuse you even further: the similar sounding 'entomology' has nothing to do with language, rather with bugs - 'entomon' means insect in Greek, and 'entomology' is the study of insects. The Greek 'temnein' means to cut (as in anatomy), as the Latin 'secare' (like in insect), and insects indeed have a tripartite body that looks as if it is sectioned into three parts. In German there is an infrequently used word for insects, 'Kerbtier', which literally means 'animal with a notch'. Nice, isn't it? I admit that this has only marginal relevance to the veterinary sciences, except for parasitologists.

I had a request from Jerry Masty (Associate Professor Veterinary Anatomy, Ohio State University Columbus, USA), who wrote: 'Read your column about etymology on the website and found it very interesting. It reminded me of a question from a student that I cannot answer. Is there an appropriate Latin/Greek based root or term to describe 'head tilt'?

In answering this question, I very much appreciate the help of Professor Wim Weijs, an anatomist in the veterinary faculty at the University of Utrecht, whose ponderings resulted in the following reaction:

'Definitions of anatomical terms for movement stem mostly from human anatomy. There, spinal rotation is defined as rotation about a longitudinal axis through the spine. For the cervical spine, this leads to saying 'no' by head shaking, making the ears face obliquely forward/backward. One can also move one's head from left to right, making the ears face upward/downward. I would define this as a human head tilt. The movement axis is now perpendicular to the cervical vertebral column and is directed forward/backward (antero-posterior). Anatomists usually call this movement laterodeviation. The third possible axis of rotation, of no consequence for tilt, is the transverse one (latero-medial); it produces flexion/extension of the neck and head (nodding 'yes') and the movement is the same in all animals. The problem is that dogs carry their head on an obliquely positioned cervical spine. To investigate the consequences, we can first look at a snake, carrying its little venomous head in front of a (usually) horizontal spine. Now the situation is reversed when compared to humans: spinal rotation (about a horizontal, longitudinal axis) leads to head tilting, while laterodeviation (about a now vertical antero-posterior axis) makes the head move from left to right, but without a tilt, e.g. both ears remain orientated horizontally.

A dog has an obliquely oriented cervical spine. As a consequence, the movements of the head as a result of rotation and laterodeviation, respectively defined on the basis of the orientation of the spine, cause displacements of the head intermediate between snake and human. After a cervical rotation bringing the head to the left, the left ear faces backward, but also upward. After a laterodeviation of the cervical spine to the left, the left ear faces backward, but also downward. I suggest a simulation experiment with a matchbox (head) and pencil (spine).



I conclude that a head tilt can be produced by either a rotation or a laterodeviation of the cervical spine, or by both at the same time. In the latter case that tilt might become 'pure' as the ear may end up facing neither backwards nor forward. The combination of anatomy and physics can be tiring, but I hope this answers the question. A torticollis is defined as the extreme and chronic rotation of the cervical spine. An opisthotonus is the chronic extreme extension of the head.'

I had another request, from Dr. David M. White, who wrote the following: 'Not exactly a word root issue, but I've been puzzled for a long time about the use of the term 'gauge' in needle sizes. I went on a lark once and tried to figure it out, and I found that gauge in relation to shotgun pellets has a distinct definition, which relates to both diameter and weight, and gauge with regard to rail track also has a defined distance associated with it. However, there is no mathematical relationship between the 'gauge' of a needle and its interior or exterior diameter, or even the weight/thickness of a metal used to construct the needle - at least not one that I could find. Any help would be appreciated - one of those little things that gnaws at you...'

The etymology of 'gauge' can be traced back to 15th century Middle English and before that to Old North French. Apart from the distance between the rails of a rail track, the word - sometimes also written as 'gage' - indeed refers to the inner diameter of a shotgun's barrel, expressed as the number of lead balls just fitting that diameter required to make a pound, e.g. 'a 12-gauge shotgun'. More generally, it is a linear measurement according to some standard, like the diameter of wire or of hypodermic needles. Also, the fineness of a knitted fabric, as expressed by the number of loops per unit width, is related to the diameter of the needles, and there are other uses, from mechanics (strain gauge) to quantum electrodynamics and chromodynamics, both examples of 'gauge theories'.

With respect to hypodermic needles, gauge is an industry standard, and the following conversions apply:

Gauge	Outer diameter (mm)	Outer diameter (inch)
20	9.02	0.355
21	8.13	0.32
22	7.11	0.28
23	6.35	0.25
24	5.59	0.22
25	5.08	0.2

(I calculated the dimensions from The Vita Needle Company, where inner diameter and tolerance data can also be found)

But back to words. In the last Etyrminology column I promised to trace some biomedical eponyms, from Abortus Bang to Zebrina, and I will do so by interspersing non-eponyms, for your entertainment and guesswork.

Anthrax: means simply coal in Greek, thus is no eponym. The infamous Bacillus anthracis may cause skin lesions, that first appear as vesicles (Pustula maligna), at the portal of entry. They develop into Carbuncula contagiosa - again referring to the black appearance of the local affections - 'carbo' meaning coal in Latin.

Brucellosis: named after the microbiologist Sir David Bruce. Born in Melbourne in 1855, he studied medicine in Edinburgh, then moved to Berlin and joined Robert Koch's famous group of bacteriologists. In 1886, Bruce went to Malta as an army surgeon, where he discovered the cause of what is now called brucellosis. The 'melitensis' Brucella got its name from the island ('melita' being the Latin name for Malta). Sir David Bruce lived until 1931, making many contributions to medical science, like discovering the cause of sleeping sickness in man and its transmission by the tsetse fly.

°C: in English this is mostly pronounced as degrees centigrade, but was originally named after Anders Celsius (1701-1744), a Swedish astronomer. He first proposed the thermometer with a scale of 100 degrees between the boiling and freezing points of water. Between 1730 and 1744 he was Professor of Astronomy at the University of Uppsala. The other thermometric scales - Fahrenheit, Réaumur, and Kelvin - also carry eponymic designations. The Fahrenheit degrees scale, used mainly in Anglo-Saxon countries, has a range divided into 180 intervals, with the freezing point at 32°F and the boiling point at 212°F. The German-Dutch physicist Gabriel Daniel Fahrenheit established the scale in 1724. René Antoine Ferchault de Réaumur (1683-1757) was a French physicist and naturalist and his alcohol thermometer ranges between the freezing point of water at 0° and its boiling point at 80°. Finally, the British mathematician and physicist William Thomson Kelvin (1824-1907) introduced the absolute temperature scale carrying his name.

Dacryoadenitis: the inflammation of the lacrimal gland is derived from Greek 'dakryon', meaning tear. Adenitis comes from Greek 'aden', the gland. A sialodacryoadenitis coronavirus of rats ('sialon' Greek meaning saliva) is a notorious pathogen in laboratory animal facilities, causing outbreaks of infections characterised by corneal ulcerations, pneumonia and often a spectacular mumps-like swelling of salivary glands in the neck. The disease spreads rapidly through a colony affecting all exposed rats; other species are not susceptible.