system, the walls of the blood-vessels, the internal organs, such as the liver and spleen, the bones and the bone-marrow, contain them.  They are not, however, apparently found in the secretions of the sweat glands, but, on the other hand, they have been shown to be present in the breast milk of nursing mothers who have active syphilis.  The seminal fluid may contain the germs, but they have not been shown to be present either in the egg cells of the female or in the sperm cells of the male.

+Fate of the Germs.+—­The fate of all these vast numbers of syphilitic germs, distributed over the whole body at the height of the disease, is one of the most remarkable imaginable.  As the acute secondary stage passes, whether the patient is treated or not, by far the larger number of the spirochetes in the body is destroyed by the body’s own power of resistance.  This explains the statement, that cannot be too often repeated, that the outward evidences of secondary syphilis tend to disappear of themselves, whether or not the patient is treated.  Of the hordes of germs present in the beginning of the trouble, only a few persist until the later stages, scattered about in the parts which were subject to the overwhelming invasion.  Yet because of some change which the disease brought about in the parts thus affected, these few germs are able to produce much more dangerous changes than the armies which preceded them.  In some way the body has become sensitive to them, and a handful of them in course of time are able to do damage which billions could not earlier in the disease.  The man in whom the few remaining germs are confined largely to the skin is fortunate.  The unfortunates are those who, with the spirochetes in their artery walls, heart muscle, brain, and spinal cord, develop the destructive arterial and nervous changes which lead to the crippling of life at its root and premature death.

+Variations in the Behavior of the Germ of Syphilis.+—­Differences in the behavior of the same germ in different people are very familiar in medicine and are of importance in syphilis.  As an example, the germ of pneumonia may be responsible for a trifling cold in one person, for an attack of grippe in the next, and may hurry the next person out of the world within forty-eight hours with pneumonia.  Part of this difference in the behavior of a given germ may be due to differences among the various strains or families of germs in the same general group.  Another part is due to the habit which germs have, of singling out for attack the weakest spot in a person’s body.  The germ that causes rheumatism has strains which produce simply tonsillitis, and others which, instead of attacking joints, tend to attack the valves of the heart.  Our recent knowledge suggests that somewhat the same thing is at work in syphilis.  Certain strains of Spirochaeta pallida tend to thrive in the nervous system, others perhaps in the skin.  On the other hand, in certain persons, for example, heavy drinkers, the nervous system is most open to attack, in others the bones may be most affected, in still others, the skin.