324 MR TURNER ON THE THYMUS AND 
University by the Marquis of BreapaLBane. It was a very large example 
of an adult male, its proportions exceeding in every direction those given 
by Dr Witttam Hunter, in his description of the Nylghau.* The thyroid gland 
was exposed in the usual way. It was found to consist of two entirely dis- 
tinet lateral halves. Each half was seated quite at the posterior part of the 
side of the air-tube, the upper end being in relation with the outer surface of 
the cricoid cartilage, the lower end reaching to the side of the fourth tracheal 
ring. The two lobes were thus separated from each other by the entire width 
of the trachea. The lobes, wide at their upper ends, gradually became narrower 
as they extended down the side of the trachea, until they terminated below 
in an almost pointed extremity. Branches from the great artery of the neck 
passed both to the upper and lower ends of each lobe. On the anterior sur- 
face of the trachea, as well as on the crico-thyroid membrane, in the interval 
between the lobes of the thyroid, scattered lobules of glandular tissue of a slightly 
reddish tint were seen. These were not connected with the thyroid, but were 
lying in the cellular tissue between its lobes. Extending for some distance down 
the front of the trachea, scattered lobules of a similar glandular substance were 
found, separated from each other by varying intervals. About thirteen inches 
above the sternum the gland-lobules became much more closely connected together. 
and formed two long lines of glandular tissue which extended downwards on the 
front of the trachea. Immediately above the sternum they became wider, and, in 
this manner, passed beneath that bone for a short distance, lying in front of the 
great blood-vessels. Small arteries derived from the carotid trunk passed to this 
long line of gland-substance. This gland, from its position, was evidently the 
thymus, the lobules of which, closely aggregated together below, were separated 
from each other by varying intervals at the upper part of the trachea, some even 
extending as high as the crico-thyroid membrane. It was thus brought into 
close relation to, although not actually in contact with, the thyroid. 
A microscopic examination satisfied me that it was the thymus,—the great 
bulk of the gland being composed of collections of small colourless corpuscles, 
about the size of, or a little larger than, the red corpuscles of human blood, arranged 
in a distinctly lobular manner. In some parts of the gland were scattered about 
highly refracting globular particles of varying size, probably fat. They presented 
a more granular aspect than is usual with oil-globules. Lying here and there in 
the connective tissue between the lobules of the gland were numerous crystals, 
sometimes ageregated together in irregular masses, at others arranged in lines, 
and in some cases scattered about in an indefinite manner. These crystals were 
all of a prismatic shape, many of them distinctly three-sided, presenting a close 
resemblance to the crystals of the ammoniaco-magnesian phosphate occasionally 
* Philosophical Transactions, 1771. 

