Response of Tissue of the Intima to Injurious Agents. ∗

Abstract

A series of experiments was designed to investigate the nature of the reaction exhibited by the intima when brought in contact with an injurious agent. Eleven arteries in 8 dogs were subjected to the experiment. The common carotid artery was isolated and doubly ligated according to the procedure previously outlined. 1 Various strengths of turpentine, ranging from 15% in mineral oil to the crude substance, and 30% to 75% croton oil in mineral oil were injected into the lumen of the vessel by syringe or through a cannula. The injurious agent was allowed to remain in contact with the intima for periods varying from 2 minutes to 48 hours and then the portion of the artery between the ligatures was removed for microscopic examination. As controls, to determine how much reaction was caused by the operative procedure alone, histological preparations were made of the arteries which were used in the phenolsulphon-phthalein experiments. 1 In these the endothelium was uniformly intact and well stained. The muscular, elastic and fibrous tissue elements of the media showed no changes. There was no necrosis or hemorrhage in any of the coats and no exudate at any point in the vessel wall proper. Surrounding some of the vessels lying in the connective tissue outside the adventitia were small collections of polymorphonuclear leucocytes, but in no instance were these seen infiltrating the adjacent tissue. Microscopic examination of the arteries exposed to an injurious agent showed destruction of the endothelium lining the vessel. In the instances where the weaker dilutions of turpentine were employed, poorly stained remnants of this layer could be seen, but with the other injurious agents it was completely absent. When 50% and 75% croton oil and higher dilutions of turpentine were used the nuclei of the muscle cells in the inner third of the media were pyknotic and a slight fraying of the elastic fibers in the media, including the internal elastic lamella, was present.