SKELETON. 



629 



(4) of the lateral mass of the sacra! vertebra 

 (BJ^/%. 448.), which causes the human anatomist 

 to name this anterior nucleary appendage as 

 the " peculiarity " of sacral form. This 

 anterior nucleus of the sacral lateral mass, I 

 call a rudimentary rib abutting against the 

 iliac bone. 



PROP. X. The coccygeal vertebra are de- 

 prived of their costal appendages. The serial 

 order in which we find all spinal figures 

 standing, renders it, under comparison, a de- 

 monstrable fact, that the coccygeal bones 

 ( B > fiS' 449.) are the debris or metamorphosed 



F,g. 449. 



remains of true and complete vertebrae, such 

 as A of the thorax. It matters not as an ob- 

 jection to the truth of this idea of coccygeal 

 bones being the minus proportionals of full 

 costo-vertebral quantities, that we now find 

 them wanting many of those elemental pieces 

 which are existing to these latter. For though 

 it be true that it is impossible now to read the 

 same number of elements in the last caudal 

 ossicle (B) which we find elsewhere posited 

 for all other vertebrae of the spinal series, yet 

 I hold it to be also impossible for any ana- 

 tomist to contempla f e the presential character 

 of a caudal bone and remain unproductive of 

 the idea that the caudal bone (B), as a cen- 

 trum (5), is a proportional left standing after 

 the metamorphosis of all its other parts. If, 

 then, we agree to this, we must also agree to 

 the fact that those very parts (1, 2, 3, 4, of A) 

 which a caudal centrum (such as B) wants, 

 are identical with those same parts which are 

 left standing to other vertebrae. Now, when 

 I find that a coccygeal ossicle (B, 5) holds 

 series with the centra (5) of all other vertebra?, 

 I have every reason to name it as being the 

 centrum of its own vertebra, which has under- 

 gone metamorphosis ; and therefore I may 

 conclude that the plus original of the caudal 

 ossicle (B, fig. 449.) is equal to A, or to any 

 other vertebra of the spinal series. It will be 

 sufficient to the present argument, which 

 holds comparison in order to establish the 

 ideas of original or archetype uniformity, that 

 we clearly understand how the original or 

 archetype of a coccygeal bone is equal and 

 uniform with any other vertebra of the spinal 

 axis. The coccygeal bones (B) as nature pre- 

 sents them to us are vertebral centra, having 

 had subtracted from them their spinous (1), 

 neural (2), and costal elements (4); and un- 

 der this interpretation we nay have as strong 

 an idea of the whole or plus quantity (A) of 

 which caudal bones (B) have been metamor- 

 phosed, as if we saw those quantities still per- 

 sisting entire. The difference between any of 

 the costo-vertebral spinal segments and a 



caudal bone is like the quantitative difference 

 between a-\-banda b. Thus A,fig. 449., minus 

 the elements 1, 2, 3, 4, equals B ; while B 

 plus the elements 1, 2, 3, 4, equals A. 



PROP. XI. The first seven thoracic costo- 

 vertebral figures are ivhole or plus quantities. 

 In no one respect do the first seven thoracic 

 costo-vertebral figures (all equal to fig. 450) 

 differ from each other ; in each of them may 

 be counted the same elemental pieces ; and 

 those pieces of each (marked as inj%.450.) are 

 identical or homologous both as to position, 

 use, mode of growth, number, and linear 

 order. These elements consequently bear the 

 same name in each, and most properly, be- 

 cause the corresponding pieces of each are 

 absolutely similar. Consequently, also, the 

 whole quantities (suchas^g. 40.), which are 



Fig. 450. 



compounded of those pieces (I, 2, 3, 4, 5, 6, 

 7), should properly bear the same name ; 

 and therefore I call them sterno-costo-verte- 

 bral circles. There are, then, seven whole seg- 

 ments (such as fig. 449.) of the human spinal 

 axis, which absolutely resemble each other in 

 quantity. These segments are posited in 

 linear order, and by this arrangement they 

 yield an absolute linear uniformity. Such 

 linear uniformity is evidently the result of 

 quantitatively equal figures being posited in 

 serial order ; these figures enclose the thoracic 

 space completely ; and, because the}' severally 

 manifest an equal number of homologous ele- 

 ments, so is it impossible to read any condi- 

 tion of specific variation between them. As 

 archetypes, or whole quantities, of the mam- 

 mal spinal axis, these seven thoracic sterno- 

 costo-vertebral figures have no special di- 

 versity. When we compare them with one 

 another we discover no more distinction 

 between them than we find between the serial 

 quantities a-\-b, a-\-b, a-\-b. It is quite true, 

 therefore, that there is at least one regional 

 department of the mammalian spinal axis, to 

 which we may apply the name of absolute 

 uniformity, as fittingly as we might apply it to 

 a linear series of circles. And it is, moreover, 

 true that the thing called species is, so far as 

 regards this linear series of plus thoracic 

 figures, as perfectly absent, as if it were non- 

 existent everywhere. But )et it is possible 

 for nature to work specific variety from out of 

 this linear series of thoracic archetypes (such 

 as fig. 450.). And how may nature effect this ? 

 Just in the same mode as she effects it in 

 the creation of skeletal bodies comparatively 

 contemplated, and this mode is the sub- 



s s 3 



