ANTHRAX 317 



cultures become turbid in thirty-six hours, with nebulous masses of 

 threads matted together. The pellicle which forms on the surfaces 

 affords an ideal place for spore formation. Cultures in the deptli 

 of gelatine show a most characteristic growth. From the line of 

 inoculation delicate threads and fibrillee extend outwards horizontally 

 into the medium. Liquefaction commences at the top, and eventually 

 extends throughout the tube. On gelatine plates small colonies 

 appear in thirty-six hours, and on the second or third day they 

 appear, under a low power of the microscope, not unlike matted 

 hair. The colonies after a time sink in the gelatine, owing to lique- 

 faction. On potato, agar, and blood serum the anthrax bacillus 

 grows well (Plates 17 and 22). 



Channels of Infection. 1. The Alimentary Canal. — This is the 

 usual mode of infection in animals grazing on infected pasture land. 

 A soil suitable for the propagation of anthrax is one containing 

 abundance of air and proteid material. Feeding on bacilli alone might 

 possibly not produce the disease, owing to the germicidal effect of 

 the gastric juice. But spores can readily pass uninjured through 

 the stomach, and produce anthrax in the blood. Infected water, as 

 well as fodder, may convey the disease. Water becomes infected by 

 bodies of animals dead of anthrax, or, as was the case once at least 

 in the south-west of England, by a stream passing through the 

 washing-yard of an infected tannery. Manure on fields, litter in 

 stalls, and infected earth, may all contribute to the transmission of 

 the disease. Darwin pointed out the services which are performed 

 in superficial soils by earthworms bringing up casts ; Pasteur was of 

 opinion that in this way earthworms were responsible for continually 

 bringing up the spores of the anthrax bacillus from buried corpses 

 to the surface, where they would reinfect cattle. Koch disputed this, 

 but more recently Bollinger has demonstrated the correctness of 

 Pasteur's views by isolating anthrax contagium from 5 per cent, of 

 the worms sent him from an anthrax pasture. Bollinger also 

 maintains that flies and other insects may convey the disease from 

 discharges or carcases round which they congregate. 



Alimentary infection in man is a rare form, and it reveals itself 

 in a primary diseased state known as mycosis intestinalis, an inflamed 

 condition of the intestine and mesenteric lymph-glands. 



2. Through the Skin. — Cutaneous anthrax, when it occurs in the 

 human subject, goes by the name of malignant pustule, and is caused 

 by infective anthrax matter gaining entrance through abrasions or 

 ulcers in the skin. This local form is obviously mostly contracted by 

 those whose occupation leads them to handle hides or other anthrax 

 material (butchers and cleaners of hides), and it naturally affects the 

 skin of the hands, forearms, face, or back (as it occurs amongst hide- 

 porters). Two or three days after inoculation a red pimple appears. 



