6 THE SKELETON OF THE CAT. 
of the centrum immediately preceding is not marked by any 
part of it. In the eleventh thoracic vertebra each costal facet 
is usually still confluent with the smooth cranial end of the 
centrum. In the twelfth vertebra the facets are separated by 
smooth ridges from the cranial end of the vertebra, while in 
the thirteenth vertebra they are separated by rough ridges. 
The spinous processes (a) of the first four are of about the 
same length. They then decrease in length to the twelfth, 
while the twelfth and thirteenth are slightly longer than the 
eleventh. The first ten slope more or less caudad, while the 
spinous process of the tenth (anticlinal) vertebra is vertical 
and those of the eleventh, twelfth, and thirteenth point craniad. 
Each of the transverse processes of the seventh thoracic 
vertebra shows a tendency to divide into three tubercles; one 
of these is directed craniad, the mammillary process (or meta- 
pophysis), one caudad, the accessory process (or anapophysis), 
while the third (transverse process proper) looks ventrad and 
bears the transverse costal facet. This division becomes 
more prominent in the succeeding vertebre, being most 
marked in the ninth and tenth. In the eleventh, twelfth, and 
thirteenth vertebre the mammillary (g) and accessory (/) 
processes are very. pronounced, while the transverse costal 
facet and that part of the transverse process which bears it have 
disappeared. The ribs of the eleventh, twelfth, and thirteenth 
vertebrze are thus attached to their respective centra by their 
heads alone. ; 
The cranial articular processes (0) are prominent on the 
first two thoracic vertebra; back of these they are very small 
as far as the eleventh, so that the articular facets seem to be 
borne merely upon the dorsal surface of the cranial edge of the 
laminz. In the eleventh, twelfth, and thirteenth the cranial 
articular processes are large, bearing the articular facets on 
their medial surfaces, while the mammillary processes appear 
as tubercles on the lateral surfaces of the articular processes. 
The caudal articular processes (/) are prominent in the first 
thoracic, then smaller until the tenth is reached; in the tenth, 
eleventh, twelfth, and thirteenth they are large and their facets 
are borne laterally, so as to face the corresponding cranial 
