SPIRILLUM 527 



cultures into pregnant cows may be followed by disease of the foetal membranes (Smith 

 1919). 



A closely related organism, named Vibrio jejuni, has been described by Jones and Little 

 (1931), and Jones, Orcutt, and Little (1931). It appears to be responsible for a disease 

 of calves and older cattle, which may occur in epidemic form during the autumn and winter 

 months, and is known as ivinter dysentery or black scours. The organisms are most 

 abundant in the jejunum. 



SPIRILLUM 



Definition. — Spirillum. 



Rigid rods of spiral form, varying considerably in the number, length, and 

 breadth of the spirals. Usually motile by means of a tuft of polar fiagella (5 to 

 20), which are mostly semicircular in shape. The flagella occur at one or both 

 poles ; their number varies greatly, and is difficult to determine, since in stained 

 preparations several are often united into a common strand. Generally Gram- 

 positive. Some species form a reddish-yellow, or greenish-yellow pigment. Found 

 in water or putrid infusions. 



Type species. Spirillum undula. 



Not many organisms in this group have been described. One of the best known 

 is Spirillum ruhrum, which was isolated by Esmarch (1887) from a mouse that had 

 been decomposing for 3 months under water. 



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1 i 



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1 



Fig. 105. — Spirillum rubrum. 

 From a broth culture, 2 days, 30° C. ( X 1000). 



Morphologically the spirilla show considerable variation. Their length may 

 vary from 1 to 50 ^, and the number of spirals from 1 to about 50. The length 

 of the individual spiral varies according to the species of organism ; in some spirilla 

 the spirals are close set, each one being not more than about 1 ju in length ; in 

 others they are looser, and may be 10^ or so in length. The width of the organisms 



