C. STOUT AND F. BOHORQUEZ 
849 
Figure 5.— (Z 316) Peacock (Pavo cristatus). Adult 
male. 
A. Atheromatous plaque showing central necrosis 
and accumulation of lipids. H & E x 25. 
B. Higher magnification showing central necrosis, 
cleft-like spaces and foam cells. H & E x 160. 
(Reproduced with permission from Exp. Molec. 
Path., Academic Press, New York). 
The cerebral arteries were not systematically 
studied in the brains of the other species of 
mammals and birds. 
DISCUSSION 
The findings in the aortas of the various spe- 
cies of captive mammals and birds are interest- 
ing for several reasons. As more and more sur- 
veys of this type are reported, it becomes clear 
that fatty streaks, fibrous plaques and athero- 
sclerotic plaques occur in a large number of di- 
verse species. In our material, and also that of 
Vastesaeger^ and Finlayson,i° true athero- 
sclerotic plaques with areas of central necrosis 
and lipid and/or cholesterol accumulations, 
were seen much more commonly in birds than 
in any of the mammals or reptiles except for 
man. This may be due to the fact that birds 
have higher blood pressures^* than mammals, 
and also higher serum cholesterol levels,^-^" al- 
though admittedly, information on both of these 
parameters is limited. It does seem certain that 
being a bird is more important than the type of 
diet consumed, since fish eating birds have far 
more atherosclerosis than fish eating mammals, 
and carnivorous birds have far more atheroscle- 
rosis than carnivorous mammals. Furthermore, 
there does not appear to be any significant dif- 
ference in the prevalence and severity of ather- 
osclerosis among the birds themselves, whether 
the habitual diet is meat, fish, grain or insects. 
The above statements are not intended to say 
that fish eating and carnivorous mammals have 
no arterial lesions. Fibrous plaques were com- 
mon in these species, especially the harbor seals 
(Phoco vitulina) and the sealions (Zalophus 
calif ornianus) , three of whom had 10% of their 
aortas involved by these lesions. It was interest- 
ing that these fibrous plaques, which resembled 
early human proliferative lesions in morphol- 
ogy and distribution, contained no Sudan IV or 
Oil Red 0 positive material. Moreover, the aor- 
tas of seals and sealions were completely devoid 
of fatty streaks. In view of the current theories 
of atherogenesis, one is tempted to conclude 
that this lack of arterial lipid is due to the fa- 
vorable ratio of unsaturated to saturated fats in 
the diet. While this may be true, it will be of lit- 
tle consolation to those who feel that prolifera- 
tion of smooth muscle cells in the intima in ath- 
erosclerosis is due to the accumulation of lipid 
within these cells. Several of the fibrous plaques 
in sealions had reached a thickness equal to the 
aortic media without the aid of stainable lipid 
(Figure 15), 
Although it is risky to extrapolate from dis- 
ease of animals to those of man, the hoofed 
mammals (Orders Artiodactyla and Perissodac- 
tyla) were another group in which lipids ap- 
