51 THORACIC AND LUMBAR VERTEBRAE. [CHAP. 



usually but 16. The Gibbons (Hylobates) and Spider 

 Monkeys (Ateles) have mostly 18. Among the Lemurina, 

 Loris and Nycticebus have as many as 23 or 24. 



Of thoracic vertebrae, the Gorilla and Chimpanzee have 

 13, the Orang 12, the Gibbons usually 13 ; other Old World 

 Monkeys mostly 12 ; the American Monkeys from 12 to 15 : 

 the Lemurs from 12 to 16. 



As a general rule the vertebral column, taken as a whole, 

 is straighter than it is in Man, showing- a much less marked 

 sigmoid curve. 



Except in the anthropoid Apes, and a few others, the 

 spinous processes of the anterior thoracic vertebrae lean 

 backwards, and those of the lumbar and some of the 

 posterior dorsal vertebras forwards, so that they converge to 

 a point near the hinder part of the thoracic region, some- 

 times called " the centre of motion " of the vertebral column. 1 

 This may be between two vertebras, but more often there is 

 one, which has an upright spine, towards which the others 

 are directed ; this is the " anticlinal vertebra." It is at this 

 point that the thoracic vertebrae begin to change their 

 characters, and assume those of the lumbar vertebrae ; and 

 the simple elongated transverse processes break up as it 

 were into the metapophyses, anapophyses, and lumbar 

 transverse processes, all of which are conspicuous in these 

 animals. 



The transverse processes of the lumbar vertebrae are 

 usually placed lower on the sides of the vertebras than 

 in Man. 



In Galago the hinder edges of the neural spines of 

 the lumbar vertebrae bear a pair of backward-projecting 



1 This disposition of the spines of the trunk vertebrae is still more 

 marked in many of the inferior mammals, especially the terrestrial 

 Carnivora. 



