sumption the bacillus finds its food prepared for it in the unhealthy state of the blood and tissues altered by the poisons that have been rebreathed from foul air so also must it be in pneumonia; if we are to accept the statements made about the bacterium of pneumonia (Crookshank, page 273). Secondary pneumonia, which is a lung attack resulting from the poison in the system from such a fever as typhoid, throws some light upon this matter, and seems exactly to explain the origin of ordinary pneumonia. In ordinary pneumonia we believe that it would be found that the person attacked had been living in rooms where the air was tainted, had breathed consequently, again and again, the exhaled poisons, until these poisons had so altered the tissue as to allow the bacterium to form its lodgment; in other words, that he was as much "poisoned" as the person suffering from secondary pneumonia. Of course a slight chill, by arresting the action of the skin and thus increasing the poison in the system, is likely enough to be the immediate precursor of the attack by rendering the conditions still more favorable for the germ. Again, latent pneumonia in quite young children is sometimes masked (Quain, page 880) by the signs of the nervous disorder which precedes it. This nervous disorder tells the story. It is caused by the poisons which are acting on the system, and which at last produce the attack of pneumonia.
It might, however, be urged that a person leading a healthy outdoor life might, after severe exposure, be attacked by pneumonia. Certainly, and in his case the attack would mean poisoning (that is, predisposing for the germ by poisoning) through the skin; just as in the case of the man living in bad air it would mean poisoning through the air taken into the lungs.
Now, granting that this is a true explanation, that pneumonia, or even common cold, is a case of poisoning, and only a case of cold in a secondary sense, it is worth noticing that the effect of these poisons must be felt in the throat and bronchial passages and lungs much more than in other organs. These poisons would cling to the sides of the throat and bronchial (and nasal) passages, and would often enter the lungs. In the case of persons living in foul air, these organs, being more exposed and in intimate contact with the poison, would probably be saturated with it, and therefore would be always prepared for disease. We can then under-
- If on the other hand it is believed that pneumonia can arise without the intervention of the bacterium, we must regard it as a case of direct instead of indirect poisoning. That there is such direct poisoning we know from those attacks of the liver and kidneys which follow a severe chill, and throw back the poisons, which should have been excreted by the skin, on to those organs. Parkes (p. 164) strongly believed that bronchitic affections are often produced from the breathing of foul air. He does not, however, as far as we are aware, enter into explanations.