On a method of producing chronic focal lesions in animals

Celloidin capsules are made by a method first used, we believe, by Dr. Clarke of the College of Physicians and Surgeons, though we are not sure of this, but certainly not entirely original with us. Small balls or globes of sugar in the form of some of the more commonly purchasable candies, are stuck to small silk threads with a hot forceps. These are dipped three or four times in celloidin, hardened for a short time in alcohol, and thrown into a jar with running water. The sugar diffuses in the course of ten or twelve hours, and a completely closed capsule is left. With a fine needle a hole is punctured through the capsule, the water drained out, and agar, inoculated with streptococci or other organisms desired, is injected into the capsule and allowed to harden. The puncture-hole is left open. The capsule is then dropped into the peritoneal cavity of a rabbit and the rabbit sewed up. In most cases the rabbits live for months. Some of them gradually emaciate, others will develop agglutinins. We have opened a number of rabbits from six weeks to four months after the capsule had been placed into them. In one case a rabbit into which the capsule had been placed in July was opened in the middle of November (over four months) and the capsule was found to contain living streptococci at this time. Apparently the organisms in the capsule are to some extent protected against phagocytes, and other protective factors. The capsules are usually surrounded by fibrin and strands of connective tissue, and lie in a membrane of tissue that has grown about them.

Incidentally, it has been noticed that in the case where the capsule had remained in place four months, the organisms were, at the end of this time, culturally and morphologically identical with the ones that had been put in, which furnishes some evidence, at least, against the mutations of streptococci in the animal body advocated by Rosenau.