Abstract
It has been shown by many experimenters that segments of blood vessels may be transplanted to other vessels, in animals either of the same or of different species, and continue, for a certain period of time at least, to fulfil all physiological requirements. Various changes may be noted in the gross appearances of the transplanted segments, depending on the vessel transplanted, the site of transplantation, and the animal into which the implantation takes place, whether of the same or different species, closely or distantly related.
A segment of a rabbit's aorta was placed in the carotid of a dog, by the Carrel method of suture, and removed at the end of seventy days. The mechanical function of the vessel was perfect. The lumen was moderately dilated, and the walls slightly thinned. Upon microscopical examination, however, the normal structure of the transplanted segment had almost entirely disappeared. The intima had disappeared, being replaced by a layer of hyalin fibrin and blood; the muscular elements had either disappeared or been greatly reduced in number, while the various layers had been the seat of many fine hemorrhages, which showed as small masses of hyalin fibrin into which new connective tissue had penetrated. New fibrous tissue had replaced the whole structure of the vessel wall to a marked degree. The striking change, however, was the absolute disappearance of all the elastic tissue in the transplanted segment. Sections stained by Weigert's elastic tissue stain showed no elastic tissue in the piece of rabbit's aorta, while that in the carotid of the canine host was normal and ran up to the line of suture, where it stopped abruptly.
The entire disappearance of elastic tissue has not been observed in segments transplanted from one animal to another of the same species.
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