Spontaneous Lesions in the Rabbit. 109 



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The early stages of the spontaneous arterial lesions in the rabbit. 

 By ISAAC LEVIN and JOHN H. LARKIN. 



\From the Department of Pathology of Columbia University, at the 

 College of Physicians and Stirgeons.~\ 



Since the first publication of Josue in 1903, who succeeded in 

 producing artificial arterio-sclerosis by intravenous injection of 

 adrenalin, a great deal of work has been done on the subject. 

 Successful results were reported by treating animals with digalen, 

 barium chloride, hydrastin, nicotine and a number of other sub- 

 stances. The lesions thus produced resemble closely the ather- 

 omatous degeneration in the human aorta. 



The site of the lesion is usually the ascending portion or the 

 arch of the aorta. The process occurs primarily in the media of 

 the vessel wall and consists in necrosis of the smooth muscle cells, 

 thickening and breaking up of the elastic fibers, and the appear- 

 ance of calcareous deposits in the diseased areas. 



All these successful experiments with the production of arti- 

 ficial arterio-sclerosis were obtained only in rabbits. All efforts 

 to produce similar results in other laboratory animals failed. 

 The question consequently suggested itself whether the success 

 with the rabbit is not due to the frequency of the spontaneous 

 occurrence of this disease in the animal. Indeed several reports 

 were made on the spontaneous occurrence of arterio-sclerosis in 

 the rabbit. A. B. Miles makes a most remarkable statement in 

 this respect. In 61 rabbits treated with adrenalin he found 

 arterial lesions in 17 animals, which represents 27.86 per cent., 

 while of 49 normal rabbits he found the same condition also in 

 17 animals, which represents 34.77 per cent. R. M. Pearce 

 found spontaneous arterial lesions in 6 per cent, of animals. M. 

 C. Hill found the lesions in 15 per cent, of 210 animals examined. 



All these investigations show that while spontaneous lesions 

 are met with in rabbits the percentage of the diseased vessels is 

 far lower than the percentage of the lesions found after treatment 

 with adrenalin and the other substances. But since all the investi- 

 gations arrived at their conclusions only by gross inspection, the 



