Our studies have thus furnished us with the key wherewith to unlock the secret chambers of auto-infection. What is that key? It is the discovery that the system may possibly absorb as high as three-fourths of this feculent substance in the colon; that this absorption is made possible by an obstructed or sluggish intestinal canal where disease germs are propagated and lodged; that these germs, along with a certain amount of excrement, invade the tissues by absorption; and that we thus have the system constantly saturated with poisonous germs and filth, re-excreted, re-absorbed and re-secreted--no one knows how many times--by the various organs of the body. That the importance of intestinal cleanliness may be better appreciated, I will quote from the following authors on the subjects of excretion, absorption and circulation of the intestinal fluids. Dr. Murchison states that: "From what is now known of the diffusibility of fluids through animal membranes, it is impossible to conceive bile long in contact with the lining membrane of the gall-bladder, bile-ducts, and intestine, without a portion of it (including the dissolved pigment) passing into the blood. A circulation is constantly taking place between the fluid contents of the bowel and the blood, the existence of which, till within the last few years, was quite unknown, and which even now is too little heeded. It is now known, says Dr. Parker, that in varying degrees there is a constant transit of fluid from the blood into the alimentary canal, and as rapid absorption. The amount thus poured out and absorbed in twenty-four hours is almost incredible, and of itself constitutes a secondary or intermediate circulation never dreamt of by Harvey. The amount of gastric juice alone passing into the stomach in a day, and then re-absorbed, amounted in the case lately examined by Grunewald to nearly 23 imperial pints. If we put it at 12 pints we shall certainly be within the mark. The pancreas, according to Kröger, furnishes 12-1/2 pints in twenty-four hours, while the salivary glands pour out at least 3 pints in the same time. The amount of the bile is probably over 2 pints. The amount given out by the intestinal mucous membrane cannot be guessed at, but must be enormous. Altogether the amount of fluid effused into the alimentary canal in twenty-four hours amounts to much more than the whole amount of blood in the body (which is 18 pounds in a man weighing 143 pounds); in other words, _every portion of the blood may, and possibly does, pass several times into the alimentary canal in twenty-four hours_. The effect of this continual out-pouring is supposed to be to aid metamorphosis; the same substance more or less changed seems to be thrown out and re-absorbed until it be adapted for the repair of tissues, or become effete."