222 TEXT-BOOK OF BACTERIOLOGY. 



rounded by a dense tangle of ray-like threads. The latter some- 

 times penetrate to a considerable distance all round and give to the 

 whole a thistle-like appearance. ' 



Stab-cultures in deep gelatin show a growth first of all at the 

 bottom of the needle-hole. A stocking-like liquefaction forms with 

 opaque gray contents. It rises gradually higher, but stops short 

 two or three fingers' breadth- from the top. Soon a plentiful de- 

 velopment of gas begins, and now the culture advances upward till 

 at last only a thin layer of gelatin at the extreme top remains free. 

 While the oedema bacilli create a decided odor, one can here per- 

 ceive nothing but a peculiar sour smell which is a characteristic 

 of the black-leg bacillus. 



In the agar cultures the bacillus thrives rapidly in the incuba- 

 tor; in twenty-four hours the food medium is filled with numberless 

 gas-bubbles, ruptured in many places, while the puncture develops 

 bacilli quite to its upper end. 



In bouillon, too, the bacilli can exist. At first thej- render the 

 liquid opaque, but soon sink in white flakes to the bottom and col- 

 lect there as- a thick sediment; at the edge or the suj-face numerous 

 gas-bubbles collect. 



If portions of the artificial cultures are transmitted to suscepti- 

 ble animals, the latter perish of black-leg. For laboratory experi- 

 ments the Guinea-pig is the most suitable animal, since it regularly 

 yields to very small portions of the virus. If we inject a drop of a 

 good bouillon culture into the subcutaneous cellular tissue of a 

 Guinea-pig, or if we put a silk thread with black-leg spores into a 

 pouch in the skin of its abdomen, death will take place in twenty- 

 four or thirty-six hours, and the post-mortem state of the body will 

 show clearly the alterations peculiar to black-leg. 



The subcutaneous connective tissue, as well as the surface of the 

 muscular system and its deeper layers, are oedematous, saturated 

 with a very abundant bloody serous fluid. Above all, however, the 

 eye is struck by the dark red, frequently almost blackish, discolora- 

 tions of the muscles in the immediate neighborhood of the point of 

 infection and for some distance around it, while the internal organs 

 offer nothing particular to notice. Examined under the microscope 

 in the hanging drop and in stained preparations numbers of rod- 

 cells are to be seen in the serum, some of which are motile and 

 possess a straight form, while others depart more or less from the 

 normal shape. A club-like swelling of one or both ends is particu- 

 larly common; sometimes one sees heart-shaped or clostridium-like 

 forms, etc. If but a short time has elapsed since death took place, 

 no spores are visible ; after a few hours the first spores make their 



