Arteriosclerosis in Birds 107 



of the extremities. It is a known fact that the vessel can be 

 affected in various ways. The disease can be a diffuse one, 

 and then the whole vessel is in an arteriosclerotic state. 

 Alternatively, the severe degeneration of the vessel — often the 

 arteria coronaria — is restricted to small defined areas. With 

 this form, we speak of a so-called arteriosclerosis in plaques. 

 Furthermore, we know — and this is another important factor 

 — that the organ has an influence on the development and 

 type of arteriosclerosis. In the brain, for example, ^ve never 

 find the same forms of vessel degenerations as in the kidneys 

 or in the heart. In the brain vessels, especially in the finer 

 vessels of the brain substance, we never find atherosclerosis 

 with deposits of fat and cholesterol esters, etc. In this organ 

 we have a more diffuse hyaline transformation, in others fine 

 fibrillar changes, a so-called fibrillar vessel degeneration, 

 similar to that which can be seen in the neuroglial tissue (of 

 the neurofibrillar changes and in the senile plaques of the 

 Alzheimer disease). This form, which Scholz (1938; Scholz 

 and Nieto, 1938) was the first to describe, is a typical mal- 

 formation of the brain vessel. The final stage is always the 

 same : the occlusion of the vessel. This occlusion is the only 

 pathological symptom which can be found. The pathological 

 process and the way of evolution can, however, vary. 



In most observations of arteriosclerosis it is not possible to 

 give a key to its origin and development. We know that 

 arteriosclerosis of the vessels of the heart, which develops 

 only in restricted areas, is often the result of an inflammation 

 whereas the diffuse forms mostly result from a primary pure 

 degeneration. Experimental studies of this disease are not 

 possible. It is possible that some types of arteriosclerosis are 

 the cause of either an acute or a chronic arteritis. The acute 

 arteritis can in turn be the result of an infection with bacteria 

 or with toxins. In the place of the inflammation of the vessel 

 wall, parietal thrombi develop. The bacterial infections may 

 disappear. After the inflammation a degenerative form 

 of arteriosclerosis may occur. An injured vessel wall, or 



