DISEASES OF THE BLOOD VESSELS 75 
aorta and pulmonary vessels. Examples will be quoted 
under the discussion of the various orders. 
Primates are not often affected with degenerative 
arterial disease, two of the instances observed showing 
this change confined to the coronary vessels. As might be 
expected the myocardium in both was affected, and in one 
animal had a definite concentric hypertrophy. A very 
interesting case was encountered in a Lion-tailed 
Macaque {Macacus silensis ). His heart showed distinct 
fibrosis of the conducting pathways from auricle to 
ventricle and of the papillary muscles. No atheroma 
was present in the aorta, but in the pulmonary distinct 
sacculations of the Monckeberg type were found. Mesial 
degeneration was apparently responsible, but no calcifica- 
tion had occurred. Death was due to acute gastritis. 
Carnivora present about half the cases seen in 
mammals and 16 per cent, of the total. Five of the six- 
teen cases owe their origin to parasitic arteritis and were 
combined with aneurysms. As will be noted by consulta- 
tion of the list there is no outstanding accompanying 
pathology, a fact which makes parasites more important. 
One case of mesial degeneration, resembling the 
Monckeberg type was observed in the thoracic aorta of 
a bear. 
Ungulata are generously represented, thirteen cases 
being recorded distributed rather unevenly between the 
odd-toed (1 or 8.5 per cent.) and even-toed groups (12 or 
2.9 per cent.). The single case in the first group occurred 
in a Zebra (Eqiius burchelli) wherein was found about 
the middle of the thoracic aorta a diffuse thickening of 
media and intima in a circular plaque approximately two 
centimetres in diameter; it was by no means so well 
developed as similar lesions in the even-toed ungulates. 
This recalls the expression of doubt by Zinserling as to 
the occurrence in the horse of arteriosclerosis similar to 
that in human beings. 
