Cause Of Smallpox

CAUSE OF SMALLPOX

The Germ an Animal Rather Than a Plant.

FAMOUS PATHOLOGIST'S DISCOVERY

Details of Dr. William T. Councilman's Interesting Researches–Life History of the Parasite, Which Is Closely Allied to the Amoeba–How Spores Disseminate the Disease.

At a meeting held the other night of the Boston Society For the Medical Sciences Dr. William T. Councilman, Shattuck professor of pathological anatomy in the Harvard Medical school, made a preliminary report on his recent discoveries as to the cause of smallpox, says the Boston correspondent of the New York Post. The work on which these deductions are based has been in progress for about two years, the evolution of the complete hypothesis being gradual.

Attention of histologists has long been drawn to certain bodies within the cells of the epidermis in smallpox separate from the nucleus, but taking nuclear stains. The early theories that these so called "cell inclusions" or smallpox bodies were protazoa and the cause of the disease found little credence and were soon generally abandoned, the prevailing opinion being that they were merely forms of degenerated protoplasm. It is these bodies, however, that Dr. Councilman has now proved to be really protozoa of a low order and undoubtedly responsible for the disease. They are not bacteria, being animals instead of plants and allied to the amoebae.

The complete life cycle of the parasite has been worked out without break in the chain by means of a long series of microscopic sections. There are two stages in the cycle, as is usual with protozoa, one asexual and the other probably sexual, though this latter point requires still further confirmation. The first stage takes place perfectly definitely in the protoplasm of the epidermal cell, the second within the nucleus itself. It is the first form which is the "smallpox body," the second, or the intranuclear form, having been previously overlooked, apparently. The stages agree perfectly with the stages of the disease, a cursory examination of a given specimen enabling an exact prediction as to the forms which will be found on minute inspection. The whole duration of both cycles, however, is a matter of only a few days, occurring early in the disease, and the parasites being in the spore stage before the usual time of death from smallpox, when the pathologist obtains his material. This accounts for the fact that the organism has been sought for through so many years without success.

The earliest appearance microscopically of the protozoan is as a small homogeneous dot within the protoplasm of the cell. This body gradually grows, without much effect upon its cell host, and at the same time becomes quite granular. It at length becomes as large as the nucleus itself, or even larger, and is quite typically amoeboid in shape. It finally grows very coarsely granular and then breaks up into many small dots or rings, exactly resembling the earliest form above. This ends the first stage of the life cycle.

Each of these small bodies is now able to reinfect a neighboring cell and repeat this same cycle, or it can infect the cell nucleus and begin on the second cycle. It has been found that in the rabbit or the cow only the first cycle takes place, no forms in the second stage having been found these animals after repeated search. This is thought to mean that this first stage, unaccompanied by the second, represents the disease vaccinia, or cowpox, the cow and the rabbit not being susceptible to true smallpox. In the monkey, however, which does have true smallpox, and of course in man, the second stage is found.

This is first seen as a very small ring within the nucleus of the epidermal cell. This ring grows, becoming meanwhile vacuolated or spongy looking, until it comes to fill up the nucleus and finally destroys it, then floating free in the degenerating tissues. This form when full grown is of considerable size, about twice the diameter of a red blood corpuscle. It is now that a sexual process is believed to take place. When ripe the protozoan is seen to be composed of a large number of small rings like the first form seen within the nucleus, and these finally separate. They are believed to be spores, existing in hardy resting stage, and are contained in the ripe smallpox pustules in countless number. When the scab dries and comes off these spores are admirably adapted to disseminate the disease by being carried everywhere. It has repeatedly been observed that smallpox infection can be carried to considerable distances by the wind alone, and this offers a satisfactory explanation of the fact.

At the conclusion of his remarks Dr. Councilman showed a series of fifty or more very remarkable lantern slides taken from photomicrographs of the specimens upon which the work has been done. In these the cells were seen to be full of these parasites in every stage described and shown in perfectly logical sequence. One slide Dr. Councilman considered particularly important. It showed a small blood vessel of the skin containing many of the small rings, the youngest form of the parasite. This indicated that the infection as universally postulated is carried to the skin in the blood. It was this specimen, found only within a few days and supplying the only link missing in the life cycle, that completed the work of two years and led Dr. Councilman to make his announcement.