Retained bullets of small calibre in the thoracic cavity were not common, unless the lodgment had occurred in the bodies of the vertebrae.
"Surgical Experiences in South Africa, 1899-1900" by George Henry Makins
Jointed to the thoracic vertebrae on either side are the ribs (r.).
"Text Book of Biology, Part 1: Vertebrata" by H. G. Wells
If the patient lands on his head, the compression fracture usually involves the lower cervical or upper thoracic vertebrae.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition." by Alexander Miles
The number of free thoracic vertebra was five in each specimen; consequently, there was no error from this source.
"Phylogeny of the Waxwings and Allied Birds" by M. Dale Arvey
A, Side view of twelfth and thirteenth thoracic vertebrae.
"The Cambridge Natural History, Vol X., Mammalia" by Frank Evers Beddard