Studies in the Pathology of Vascular Disease: The Response of the Rabbit's Carotid Artery to Injuries—Effect of Injection of Tubercle Bacilli and of Colloidal Cholesterol

Experimental.-The suspension of tuberde bacilli used was prepared by grinding a loopful (about 3 mg.) of bovine tuberde bacilli with sterile mortar and pestle and suspending them in I cc. of sterile, normal saline. The final series of observations (after exdusion of cases complicated by thrombus formation or obvious errors in technic) comprises 15 animals, autopsied at intervals of 6, 12, 24, and 72 hours, at 4 and 6 days, and at 1, 2, 3, and 11 weeks after injection. At 6 hours the perivascular tissue* shows a diffuse polymorphonudear exudate, with margination of these cells in the small vessels. The elastic and muscle tissues of the media are well preserved and there are no leukocytes within the vessel wall. The endothelium is in places detached from the internal elastic lamella. At 12 hours (Fig. 15) there is also a marked exudate in the perivascular tissue and the outer half of the media is diffusely infiltrated with polymorphonudear leukocytes. The tissues of the media show evidence of slight edema. The endothelium is slightly separated from the wall. There is no exudate in the lumen. At 24 hours (Fig. 16) the entire vessel wall is diffusely infiltrated with polymorphonuclear leukocytes, which appear to be passing through the wall into the lumen, although the elastic tissue stain shows very few breaks in the internal elastic lamella and the vessel wall in general is well preserved. The endothelium is again largely detached and the individual cells appear swollen. In the lumen are a moderate number of polymorphonuclear leukocytes and a few thin, spindle-shaped cells resembling detached endothelial cells. The 72-hour specimen shows a slightly more advanced picture. There are more polymorphonuclear cells in the lumen and the leukocytes scattered through the vessel wall show evidence of pyknosis and disintegration. The media still appears well preserved. In