copies. The later copies have a different text. It is impossible to say
_what_ kind of fastening is meant. ⁂ might be a ligament or a
vertebra—though more probably the latter. But it might be a combination
of several pieces. ⁂⁂⁂ is the occiput, and this suggests the
hypothesis of cervical vertebrae. But the number of these is not four
but seven. Of these _three_ are peculiar; the Atlas which supports the
head, the Axis upon which the head turns, and the Vertebra prominens
with its long spinal process. But see the Vignette of chapter 42 from
_Pd_ where four vertebrae are figured.