158 Dr. J. B. S. Jackson's Dissections of a 
which subdivided into, first, the subclavian; and, secondly, a 
large branch which followed the phrenic nerve, and was distri- 
buted like it upon the diaphragm, sending off a very’ small 
internal mammary artery near its origin. The left innominata 
divided mainly like the right, but the subclavian was acci- 
dentally cut off. The left superior intercostal arose separately 
from the aorta, one inch beyond the second great trunk, a 
vessel corresponding in situation being also found in the whale. 
The plexus on each side of the spine was well marked, and, 
on cutting away extensively the wings from the bodies of the 
vertebra, it was seen to pass freely into the spinal cavity, and 
completely to surround the theca, being there very strongly 
marked. In the lower part of the abdomen the plexuses were 
not so distinct. 
"The air-cells communicated, so that through one of the 
secondary bronchi the whole lung could be inflated ; in size 
they about equalled those of man, being considerably larget 
than in the whale. The muscular fibres, which have been 
described as surrounding the lungs, I did not find. The 
trachea was much flattened antero-posteriorly, and fifteen rings 
were counted on one side. Just above the bifurcation a large 
bronchus was given off to the upper part of the right lung, 
and in the substance of the lungs the rings were continue 
nearly or quite down into the smallest tubes, as has been often 
"Phe spiracle, or blow-hole, being exposed on one side by à 
longitudinal section through the skull, was found to be a regt- 
lar and continuous passage for about one half its extent UP 
wards from the fauces. The upper half was very Heg 
being dilated mainly into two large sacs, each of which 
probably hold $jss. or more, and which seemed to burrow 
beneath the skin as the finger was passed into them through 
the external semilunar orifice ; the expulsor muscles 
these sacs were very large. 
Mr. Hunter says of the cetacea generally, «J could eid 
observe anything like a thyroid gland.” It existed, boWeYe^ — 
3 
would 
