304 THOMAS DWIGHT ON 



In Class IV, Group D, in which the 24th is more or less sacralized, the 19th is on 

 the whole thoracic, but generally with lumbar or transitional features. 



In Class V, in which the 24th is the fulcralin, we find in Group A that in D-7 the IDth 

 has lumbar features and the change of the articular processes is above it, but that never- 

 theless it is reckoned thoracic. In Group B it is essentially lumbar in both spines. In 

 Group C it is clearly lumbar in 267 and transitional in 202, differing on the two sides. 



Apparently both these vertebrae are absolutely unstable. It is impossible to decide 

 the number of an isolated one. A 19th may be a typical lumbar, and a 2(lth a typical 

 thoracic. 



I do not remember to have seen mentioned the fact that when the last ribs are very 

 small or rudimentary, the pair above them is much longer than a penultimate usually is. 

 This is true whether the last pair be on the 19th or the 20th vertebra. 



Cervical, JRudimentari/ 1st Thoracic, Bicipital and Trlclpltal Rlhs. — The anomalies 

 of the region at the top of the thorax are both more interesting and more difficult than 

 those at the bottom. There we have just seen that one vertebra may perfectly resemble 

 another of a different numerical position ; here it is more doubtful. From the study of 

 these spines and the writings of others, it appears that there is at least one type of a rib 

 which is seen only on the 7th vertebra, and that there is a peculiar form of bicipital rib 

 which is seen only in the thorax. On the other hand, while several instances of defective 

 1st thoracic rib are very much alike, it is impossible to distinguish them with certainty 

 from cervical ribs. 



In this series there are ten spines and two incomplete specimens with ribs connected 

 with the 7th cervical vertebra. This includes H-3 in which it is more probable that there 

 is a suppression of a cer\acal vertebra, so that the l.st ribs, one of which is imperfect, 

 should be considered thoracic. There is one case of bicipital rib (649) . There are also 

 the following cases of defective 1st thoracic rib: G-22, not rudimentary but small, A-4, 

 H-3 (if it be not included among cervical ribs), and incomplete specimens 9379-38 and 

 572. Moreover there are the following cases of fused thoracic ribs : spine 208, tricipital ; 

 and incomplete specimen C-1, bicipital. 



Among the cer\dcal ribs (putting the doubtful H-3 aside for the present) there are 

 two cases in which their cartilages reach the sternum (267 and 202) . According to 

 Gruber's classification the most perfect form of cervical ribs has the cartilage joining that 

 of the 1st thoracic before reaching the sternum. There is, I believe, no single case on 

 record of a cervical rib having its cartilage end at the place of the normal termination of 

 the first rib, with tlie next rib ending at the junction of the manubrium and body of the 

 sternum, and the cartilages being absolutely separate.' This is what occurs in 202, on one 



1 Bolk's case had not appeared. See foot-note on p. 200. 



