636 



SKELETON. 



vertebrae of v,fig, 457., produce thecostae a b 

 of greater dimensions than ordinary, these 

 segments of the spinal axis are but resembling 

 somewhat more completely the thoracic costo- 

 vertebral archetypes (such as 8, c, d, of B, 



fig- 457.) ? 



Whenever, therefore, the sixth or seventh 

 cervical vertebra produces the cervical ribs, I 

 may interpret the occurrence of this " ano- 

 malous " fact in this way, viz. that a greatei 

 proportional of the archetype costo-vertebral 

 quantity (such as 8, c, d, of 8,^.457.) re- 

 mains to the sixth and seventh spinal segment 

 than is generally the rule. Cervical vertebrae, 

 therefore, whether with or without the plus 

 cervical ribs, are still the proportionals of full 

 thoracic costo-vertebral forms ; and the 

 number of cervical vertebras simply depends 

 upon the number and degree of metamor- 

 phosis to which thoracic costo-vertebral forms 

 have been subjected. When the cervix de- 

 velops seven vertebrae of those proportions, 

 such as we ordinarily find in the mammal 

 body (A, Jig. 456.), all we can say of it is, 

 that seven thoracic archetypes have suffered 

 metamorphosis of the ribs to the cervical 

 degree ; and when the mammal cervix ex- 

 hibits only five or six vertebrae of cervical 

 degree (e,fig. 457.), this occurs by reason of 

 the fact that the seventh vertebra of B is not 

 metamorphosed to cervical degree, but still 

 retains a large proportional of the rib (b). 

 When the mammal cervix (\,ji.g. 457., or u, 

 jig. 456.) produces nine cervical vertebra?, 

 then the simple interpretation is, that nine 

 quantities, equal to those of the thorax, and 

 which I have represented in dotted outline, 

 have had the original plus costo-sternal quan- 

 tity subtracted from them. 



PROP. XXV. The presence of cervical ribs 

 subtracts from the number of cervical vertebra:, 

 and adds to the number of thoracic archetypes. 

 Whenever cervical ribs (a, b of B,fig. 457. 

 and 458.) are produced upon the sixth and 

 seventh cervical vertebrae, the numerical 



length of the cervical region of the mammal 

 spine is diminished to the serial line of five 

 cervical segments, which we call cervical ver- 

 tebrae ; and there and then by the occurrence 

 of this fact, which subtracts from the cervical 

 vertebral numbers, the thoracic costo-ver- 

 tebral spinal region is added to and becomes 

 numerically greater than we ordinarily find 

 it. By as much as the ordinary cervical re- 

 gion is lessened, owing to the presence ot 

 cervical ribs, by so much is the thoracic 

 region increased owing to the same cause, 

 viz. the presence of cervical ribs. The con- 

 verse of this condition would happen if ribs 

 were subtracted from the thoracic spinal re- 

 gion ; and we would then find that by as 

 much as the thoracic region was lessened by 

 so much would the cervical region be in- 

 creased. What other rational interpretation 

 can be given of this condition of balancing 

 between the cervical and the thoracic spinal 

 regions except this, namely, that the nu- 

 merical difference of both regions occurs by 

 the presence or absence of full costal forms ; 

 and that the condition of either region of the 

 spinal axis is influenced by the simple law of 

 subtracting the ribs from whole thoracic 

 costo-vertebral quantities.* 



PROP. XXVI. The length of the thorax 

 depends upon the number of persistent costo- 

 vertebral archetypes. When I say that the 

 numerical length of the cervix depends upon 

 the number of costo-vertebral archetypes which 

 have undergone a metamorphosis of osseous 

 quantity down to cervical degree, it will fol- 

 low that the numerical length of the thoracic 

 region must depend upon the number of those 

 original archetype costo-vertebral figures left 

 standing in spinal series. That same law of 

 formation which influences the numerical 

 length of one spinal region must also influence 

 the numerical length of the adjacent spinal 

 regions, and so we invariably find this to be 

 the case. When the cervix of Jig. 458. pro- 

 duces cervical ribs a on the vertebiv 6, md 



Fig. 458. 



the next succeeding, the thorax is increased. 

 When the loins produce lumbar ribs, suc- 

 ceeding the vertebra 196, the thorax is still 

 increased. When the thorax is numerically 

 lessened, by subtracting the ribs a b from 

 the vertebrae 6 19, the cervical or lumbar 

 spinal regions are numerically increased. Now 

 all this variation in the spinal regions no 

 doubt depends upon the number of per- 

 sistent ribs, whether normal or abnormal. 

 The degradation of the costo-vertebral ar- 



chetype whole quantities, is the law which 

 produces all minus or special variety, and 



* As it seems that the presence or absence of the 

 costal pieces varies the quantitative character of the 

 vertebras, making them thoracic by their plus pre- 

 sence, and cervical by their almost total obliteration, 

 so the reader will, from this expression of the fact, 

 readily gather the tendency of my remarks, which 

 is this, namely, that the archetypal quantities of the 

 cervical spinal region are equal to those which are 

 still persisting for the thorax in full sterno-costo- 

 vertcbral proportions. This, be it right or wrong, is 



