1 66 
Mr. Home’s Observations to show 
At the termination of each rib is a small cartilage in shape 
corresponding to the rib, only tapering to the point. Those 
of the opposite ribs have no connection, and when the ribs are 
drawn outwards by the muscles, are separated to some dis- 
tance, and rest through their whole length on the inner surface 
of the abdominal scuta, to which they are connected by a set 
of short muscles : they have also a connection with those of 
the neighbouring ribs by a set of short straight muscles. 
These observations apply to snakes in general ; but they 
have been particularly examined in a boa constrictor, three 
feet nine inches long, preserved in the Hunterian Museum. 
In all snakes, the ribs are continued to the anus, while the 
lungs, seldom occupy more than one-half of the extent of the 
cavity covered by the ribs. These lower ribs can only be em- 
ployed for the purpose of progressive motion, and therefore 
correspond in that respect with the ribs in the draco volans 
superadded to form the wings. 
The parts of which a description has been attempted, will 
be better understood by an inspection of Plates IV. and V. than 
by any explanation that words can convey. 
In Plate VI. the joints between the vertebrae and ribs are 
represented of the natural size from the skeleton of a large 
boa, sent from the East Indies by the late Sir William Jones 
and deposited in the PXunterian Museum. On the under surface 
of the vertebra is a protuberance for the attachment of muscles 
peculiar to this genus, it varies in size in the different species, 
and explains the power attributed to the boa constrictor. 
When the snake is going to put itself in motion, the ribs 
of the opposite sides are drawn apart from each other, and the 
small cartilages at the ends of them are bent upon the upper 
surfaces of the abdominal scuta, upon which the ends of the 
