196 INFECTIVE DISEASES. 



cover-glass preparation from a potato-culture the individual segments 

 will be found to have a great tendency to be isolated one from the 

 other, and there is copious spore-formation. 



Preservation of Spores. .Spores may be preserved simply by allow- 

 ing anthrax blood to dry and then sealing it in a tube. The spores 

 from a potato-cultivation are treated as follows : The inoculated 

 surface bearing the creamy cultivation is sliced off in a thin 

 layer, and is mashed up with distilled water in a glass capsule. 

 Sterilised silk-thread is cut up into lengths of about a quarter of 

 an inch, and allowed to soak in the paste for some hours, under a 

 bell-glass. The threads are then picked out with a pair of forceps, 

 and laid upon a sterilised glass plate, covered with a bell-glass, 

 and allowed to dry. From the plate, when perfectly dry, they 

 are transferred to a small test-tube, which can be plugged with 

 cotton-wool, or sealed in the Bunsen burner. 



Examination of the Tissues. The organs should be hardened 

 in absolute alcohol, and sections prepared and stained by the 

 ordinary methods. The method of Gram is the most instructive, 

 and eosin a very satisfactory contrast stain. The capillaries in 

 the lungs, liver, kidney, spleen, skin, mucous membrane, etc., will 

 be found to contain bacilli. In some cases the bacilli are so 

 numerous that a section under a low power has the appearance 

 of an injected specimen. 



Inoculation of Animals. A thread containing spores, a drop of 

 blood from an infected animal, or a minute portion of a cultivation, 

 introduced under the skin of a mouse or guinea-pig, causes a fatal 

 result, as a rule, in from twenty-four to forty-eight hours. Sheep 

 fed upon potatoes which have been the medium for cultivating the 

 bacillus, die in a few clays. Goats, hedgehogs, sparrows, cows, horses, 

 swine, and dogs are all susceptible. Rats are infected with diffi- 

 culty. Frogs and fish have been rendered susceptible by raising the 

 temperature of the water in which they lived. Cats, white rats, 

 and Algerian sheep have an immunity from the disease. 



Attenuation of the Virus. Toussaint attenuated cultures by 

 exposing them for ten minutes to 55 0. Pasteur obtained a similar- 

 result by resorting to lower degrees of temperature ; and Koch, 

 Gaffky, and Loffler concluded from their experiments, that from 

 42 to 43 C. the bacillus was most easily deprived of its poisonous 

 properties. By cultivating the bacillus in neutralised broth at 

 42 to 43 C. for about twenty days, the infecting power is weakened, 

 and animals inoculated with it (premier vaccin) are protected against 

 the disease. To obtain a still more perfect immunity, they are 



