By Solange Schrijer and Paul Rene van Weeren The question of how the activity of the horse's back can be described best can be traced back to the ancient world. Claudius Galenus (130-200AD) developed the concept of the 'vault roof', in which the horse's back and the upper part of the thorax create a roof over the abdominal and thoracic cavity.
The spinal processes prevent the roof from collapsing, However, the fact that the spinal processes (the bony projections of the spine) normally do not touch each other, made this representation improbable. A new concept was developed in 1947 by C. Bergmann and further developed by E. Zschokke in 1892. This concept saw the back as a grid bridge on four pillars - the horse's legs. The upper fixed point is the nuchal/supraspinous ligament which withstands the tension forces. The looser fixed point - the vertebrae - are under pressure. The spinal processes and the ligaments in between constitute the smaller supports between both fixed points. This concept served as a foundation for many studies and was generally accepted until the 1940s. However, it contained on fundamental mistake. Such a bridge is stressed through tension from below and pressure from above - the opposite of how a horse's anatomy works. After thoroughly studying the anatomical shapes of the spinal processes of a variety of animals, zoologist E.J.Slijper created a model in 1946 that is still accepted today. His so-called 'bow and string' concept not only takes into account the horse's spinal column and limbs but also his sternum and abdominal muscles. P.J. Barthez had presented such an idea 150 years earlier in 1798, but apparently he was ahead of his time. This model, now agreed upon throughout the world, presents the spinal column as a bow that is held under tension by the string (the abdominal wall). In this concept, the nuchal / supraspinous ligament is stretched and loaded under tension, which is the only stress it is able to withstand. ___________________ Judy http://icehorses.net http://clickryder.com
