334 DISEASE IN WILD MAMMALS AND BIRDS 
sule vary; in places the picture is that of a carcinoma. Small, round, 
interspersed with larger irregularly shaped acini are seen lined by a 
single layer of low cuboidal epithelium. Very frequently indeed the 
lining cells contain fine granules of golden brown pigment even Avhere 
their lumina contain no blood. Some of the larger acini contain altered 
blood cells and a smooth, pink material, knife streaked and vacuolated 
peripherally. In some parts of section these acini are regular and 
well formed, in others they are very irregular and appear to be eroding 
the capsule. A second appearance concerns the connective tissue. Ap- 
pearing in almost any part of the section and bearing no regular rela- 
tion to the epithelial elements or the section in general are areas of 
closely packed large spindle cells with hyperchromatie nuclei. In 
another place such spindle cells are arranged purposefully to form 
irregular capillaries containing blood. A third appearance results from 
a combination of the first two. Here there are acini, between which 
run blood capillaries with remarkably rich and numerous embryonic 
lining cells. A section stained by Van Gieson stain proves that part 
of the pink intra-alveolar material is colloid. Every gradation can be 
made out in tint of this material from pink to salmon to orange. It 
is often very difficult or impossible to state whether a given blood- 
filled space is a blood vessel or an acinus with hemorrhage. In both 
structures the lining consists of flattened cells. In one there is the 
possibility of colloid, in the other of hematcgeneous hyaline, both 
with peripheral vacuolization. Lung shows walls of alveoli thickened 
by young type of cells. Nuclei of cells lining bronchi are prominent, 
in good condition. Much coal pigment through whole section. Air 
sacs empty. There are several rounded nodes through section con- 
sisting of closely packed spindle and round cells. Blood is abundant 
in such nodules both in small lined spaces like capillaries and in larger 
necrotic foci where there is abundant blood pigment. In one place 
an irregular, large acinus is seen containing a smooth pink material. 
A large part of the interstitial tissue is diffusely infiltrated by the large, 
round cells with hyperchromatie nuclei (Figs. 36 and 37). 
Prairie Wolf (Canis latrans) 6. Mixed tumor of thyroid. Metas- 
tases to lungs. The neck of the animal is enormously enlarged, the 
diameter exceeding that of the body. ThjToid is enormously enlarged 
to about the size of a child's head, rather firm before incision. When 
incised about 300 cc. blood stained fluid drained. It is rather soft 
and quite friable looking as if made up of fatty and hemorrhagic 
matter. The lung is of mottled deep red color with here and there on 
sixrface small hemispherical areas about the color of the surrounding 
tissue but of slightly increased resistance. They are raised above the 
surface and measure 2-7 mm. in diameter. Histological section 
of thyroid shows a mixed tumor. It is not possible to say that it is a 
pure thyroid gland tumor. It is largely sarcomatous, the round cell 
alveolar arrangement dominant at one place, at another the short 
spindle cell but not typical, so-called spindle celled type. There are 
