202 BACTEKIA. 



vorite martyr of science, the guinea pig, and cause the 

 disease. Just at present the newspapers and medical 

 journals have a great deal to say about diphtheria and 

 its treatment by the antitoxin. 



This disease which is so destructive, especially to chil- 

 dren, is due to a bacillus which resembles very much the 

 bacillus tuberculosis, though it is usually smaller. Be- 

 ing deposited in the throat it multiplies with marvellous 

 rapidity and forms a ptomaine which, being absorbed by 

 the system, leads too often to fatal results. I have told 

 you how poisonous this ptomaine is. It acts as a pro- 

 found depressant of the heart and nervous system and 

 kills usually by paralysis. I have had a patient die two 

 weeks after all symptoms of the disease had vanished. 

 I had ceased my visits and tlie child was playing about 

 the house when she fell over dead. If a small swab of 

 cotton is passed over the membrane in the throat and 

 then rubbed over the surface of some coagulated blood- 

 serum in a tube, colonies of the bacillus will be found on 

 the serum if the tubes are put in the brood oven at from 

 95° to 98° for about 18 hours. These colonies consist of 

 myriads of the bacilli and they may be transferred to 

 cover glasses, stained and examined. I will tell you of 

 the antitoxin in a few minutes. The problems presented 

 to the bacteriologist are many and puzzling, but perhaps 

 none is more puzzling than the subject of immunity and 

 susceptibility. Why is it that a culture of anthrax will 

 kill a common rat but have no effect upon a white rat ? 

 Why is it that Mr. A's family of ragged and healthy 

 looking children all die of consumption while Mr. B's 

 sickly brood die mostly of old age ; and why do cats have 

 consumption and dogs do not ? Finally, why is it that 

 we don't all die whenever an epidemic comes around? 

 It is to the solution of such problems as these that the 

 best medical thought of the day is directed, and little by 

 little clues are obtained which some day will, I doubt 



