108 S. SCHEIDEGGER 



infiltration by parasites, can often be the causative factor in 

 chronic arteritis. Domestic animals, especially cattle, dogs 

 and pigs, show a slight thickening of the arterial walls through 

 proliferations of the intimal tissue. Scherer (1944) describes a 

 case of a 20-year-old chimpanzee with sclerosis of the main 

 vessel of the brain without degeneration of the tissue. In four 

 Macacus rhesus monkeys the same author could observe fine 

 degenerations of the cortex of the brain with multiple small 

 areas showing a softening of the tissue. In the cerebellum the 

 granular layer was in a state of degeneration with multiple 

 areas in which the cells had disappeared. In birds more severe 

 forms of such degenerations can be seen. Two different 

 phenomena may be the cause : some species of birds reach an 

 advanced age, and some are (and this is another important 

 fact) purely carnivorous. The distribution and the anatomy 

 of arteriosclerosis in birds present some difficulties. In most 

 cases the aorta is the seat of the malformation. The aorta 

 valves are free of lesions. In the intima layers we often find 

 hyperplasia with an increasing of fibres. The media shows a 

 muscular granularity in this part of the vessel wall. Micro- 

 scopical examination of such vessels shows a media with 

 ruptured muscle fibres and and a split or broken elastica. The 

 intima is often covered with a fibrocellular exudate. 



One of the best and most complete reports on the problem of 

 arteriosclerosis in birds has been published by Fox (1923), who 

 gives a survey of the different types of diseases affecting the 

 animal in captivity and in the wild state. To illustrate the 

 problem the author has collected some thousands of post- 

 mortem examinations in the Washington Zoo. Psittaci have a 

 high percentage of arterial disease. Some findings are of 

 interest. Often the central vessels are not the principal seat of 

 an atheromatosis as in other classes, and the lesion shows 

 reactions with tissue proliferation. Accipitres have the great- 

 est percentage of any order. The arterial lesions are frequently 

 accompanied by renal, myocardial, and valvular disease. 

 Degenerations are equally severe in the media and intima. 



