628 
Louping III. 
parietal pericardium, and of the mediastinal connective tissue 
is present in most instances of well-pronounced disease to a 
greater or lesser degree. The pericardial fluid is increased in 
amount. 
4. The thyroid gland of the adult animal appears of the normal 
size. In its interior there are white, creamy, grumous masses which, 
under the microscope, are made up chiefly of scaly epithelial cells. 
But such creamy masses are present also in normal sheep. As far 
as the examination of sections of the gland under the microscope 
goes, the structure of the thyroid appears normal. In the lambs 
the thyroid appears also of normal size, and in structure shows no 
change ; in one lamb only was the right thyroid reduced in size (to 
about half that of the left) and showed in its substance what 
appeared as greyish streaks and patches ; under the microscope 
these greyish portions were loaded with granular masses. 
5. The liver shows in some cases congested patches, but in others 
seems normal. 
6. The spleen is small and normal. 
7. The stomach and intestines look normal ; in lambs the ileum 
is congested. 
8. The kidneys look normal. 
9. The blood is normal in its appearance and coagulability ; in 
cases only of pronounced lung disease it is of dark colour. 
Summary . — Of all the appearances that I have described, those 
affecting the brain and the medulla are the only ones which could 
account for the symptoms observed during life and for the fatal 
issue. The affection of the lungs, severe only in few cases ; and 
the affection of the pericardium, only in few cases conspicuous and 
almost absent in lambs, would not produce any notable symptom 
during life, and could not be the cause of death, so rapid in some 
cases. The actual changes of the lung and heart observed in lambs 
are in conspicuous disproportion to the severity of the illness and 
the fatal issue ; and, similarly, in sheep (except in few cases), the 
intensity and amount of the lesions in the heart and lung were of 
such a nature that they could not, in a mechanical way, account for 
the rapid death. On the other hand, the changes in the brain and 
medulla are of a nature that, by causing “brain pressure,” would be 
the very conditions which, by their rapid development and rapid 
increase in intensity, could, by mechanical means alone, readily 
cause the disease and its speedily fatal issue ; an extensive conges- 
tion of the vessels of the pia mater setting in suddenly, an acute 
copious transudation from them, and a consequent rapid increase of 
the subarachnoidal fluid would, as a matter of course, readily 
cause those motor disturbances so prominent in this disease ; while 
the increasing pressure on the medulla oblongata might, owing to 
its secondary effect on the centres of respiration and the cardiac 
centre, cause the fatal issue. 
The primary cause of the disease should then affect, in the first 
place, the vessels of the pia mater, causing therein an acute conges- 
tion, with subsequent exudation and increase of the cerebral fluid. 
