TEXT-BOOK OF BACTERIOLOGY. 203 



scalpel or platinum hook, and mix it with sterilized water in a dish 

 until a homogeneous opaque, grayish- white liquid mass is formed. 

 A number of pieces of silk thread about - cm. long have previously 

 been sterilized in a test-tube with dry or moist heat. These are 

 now laid in the spore-solution, well stirred up with it, and then 

 laid out in rows on a sterilized sheet of glass. A bell-glass pro- 

 tects them from impurities in the air, and in a few hours they are 

 completely dry and can be taken up with the forceps and preserved 

 in a safe place. They remain efficacious and reliable for years. 



We have stated that the anthrax bacilli appear in the hanging 

 drop as rod-cells of perfectly uniform transparency and with 

 slightly-rounded ends. It is otherwise, however, when we employ 

 staining solutions. As a rule, it is true, the cells take the color 

 equally in all parts. Bacilli taken from a fresh culture have, in a 

 stained cover-glass preparation, a strong resemblance to other large 

 rod-cells, for example to those of the hay bacillus, only that they 

 show decided corners and do not appear pointed at the ends like 

 the hay bacillus. 



But if the bacteria are derived from the blood or tissue fluids of 

 animals which have died of anthrax, a very peculiar behavior is 

 noticeable in the staining. Occasionally a narrow central zone in 

 the interior of the cell, running parallel to its longitudinal axis, 

 proves particularly susceptible to the stain, and stands out as a 

 dark mass from its paler surroundings, which look like its capsule 

 or halo. This effect is obtained specially by quick staining with 

 Ziehl's solution or carbol-methyl-blue, which would lead to the sup- 

 position that we have in this case a bacterial nucleus with its pro- 

 toplasmic body. 



In most cases, however, the appearance of the rod-cells in the 

 stroke-culture is different. They show no difference between centre 

 and circumference, but are striking from the very curious form of 

 their ends, which are distinctly concave. Thus it happens that 

 where two cells come together end to end, an oval free space is left. 

 As one must regard a single cell not as a flat body, but as a 

 rounded or cylindrical staff, the formation of the ends must be 

 something like that of the top end of the radius where it joins the 

 bone of the upper arm. 



When a long row of rod-cells is seen united, one is reminded of 

 a bamboo-cane, the thickenings and constrictions occurring at reg- 

 ular intervals bearing a certain resemblance to the joints of the 

 cane. 



What may be the cause of this peculiarity is difficult to decide. 

 Perhaps the membrane (which, as in other bacteria as well as the 



