MICRO-ORGANISMS IN DISEASE. 



497 



into other animals. Animals thus inoculated 

 generally die within forty-eight hours, and on 



HEART'S BLOOD OP A MOUSE DEAD OF ANTHRAX. 



microscopic examination the blood and spleen 

 are found to be teeming with the bacilli. 



Bacillus Tuberculosis. This form is found in 

 the sputum of tuberculous patients, and also 

 in deposits of tubercle, especially within the 

 lungs. Their presence may be demonstrated 

 even before the ordinary signs of phthisis have 

 been detected, so that they may furnish a valu- 

 able means of diagnosis in early stages of the 

 disease. The bacilli form spores within the 

 body, and these spores seem to retain their 

 virulence for some time after they are dried, 

 which is an argument in favor of the possi- 

 bility of consumption being communicated by 



HUMAN TUBERCULOUS SPUTUM. 



the breath. These organisms can be readily 

 cultivated in artificial media, and when an 

 animal (especially a rabbit or Guinea-pig) is 

 inoculated with fluid containing them, the 

 characteristic disease is produced. The detec- 

 tion of the tubercle-bacillus by the microscope 

 requires a good deal of careful manipulation, 

 though the original methods of staining have 

 been much simplified. The specific nature of 

 the parasite is' now almost universally admitted, 

 although further experiments are necessary 

 before the infectious character of tubercular 

 VOL. xxiv. 32 A 



phthisis can be regarded as established beyond 

 a doubt (see TUBERCLE BACILLUS, in "Annual 

 Cyclopaedia" for 1883). 



Comma-Bacillus. Under this name is under- 

 stood the micro-organism of cholera, the latest 

 addition to the parasitic forms found in dis- 

 ease. As described by Koch, the cholera- 

 bacillus is a small, curved body, bearing a 

 striking resemblance to the punctuation-mark 

 from which it derives its name. Its peculiar 

 shape, as well as the conditions under which it 

 is found, readily distinguishes it from all other 

 parasitic organisms. It is smaller, shorter, and 

 thicker than the tubercle-bacillus (for an ac- 

 count of its discovery, etc., see CHOLERA, page 

 143). These bodies are found in great num- 

 bers in the dejections and intestinal canal of 

 cholera-patients. The method of examining 



A DROP OP MEAT-BROTH, WITH PURE CULTURE OP COMMA- 

 BACILLI. 



them, as described by the discoverer, is similar 

 to that which is used in the case of the tuber- 

 cle-bacillus. A drop of mucus from the intes- 

 tines or choleraic stools is spread out on an 

 object-glass, the glass drawn several times 

 through the flame of a spirit-lamp, or Bunsen's 

 burner, and a watery solution of fuchsine is 

 added. After a few seconds, the stained speci- 

 men is examined with a high power of the 

 microscope (one twelfth of an inch, oil system, 

 with Abbess condenser), when the parasites 

 are readily seen. The bacilli may be cultivated 

 by placing a drop of the same mucus in food- 

 gelatine, which has a weak alkaline reaction. 

 The liquid gelatine is then poured upon a glass 

 plate, beneath which is some pounded ice, and 

 the gelatine soon freezes ; the plate is then put 

 under a glass receiver, where it is kept moist 

 until the bacteria develop. Milk also is a good 

 culture-fluid. They flourish best at a tempera- 

 ture between 86 and 104 Fahr. ; they cease to 

 grow below 67 F. If exposed to a frost, they 

 are temporarily disabled, but can be revived 

 even after an hour's interval. Under the mi- 

 croscope the bacilli present an animated pict- 

 ure, moving in all directions across the field, 

 14 like swarms of dancing midges," as Koch ex- 

 presses it. 



The cholera-germs cease to grow when air 

 is removed, or after they have been dried for 

 about three hours. They grow, but with diffi- 

 culty, in fluids having an acid reaction. Cer- 

 tain substances kill the bacilli, such as strong 

 solutions of iodine, sulphate of iron, or cop- 

 peras (2-per-cent. solution), carbolic acid, 1 to 

 400; oil of peppermint, 1 to 2,000; sulphate 



