202 AIDS TO BACTERIOLOGY 



In addition to diseases already mentioned, Cockayne 

 gives the following list of diseases proved or suspected 

 on strong grounds to be due to a filterable virus: African 

 horse sickness and the nearly allied catarrhal fever of 

 sheep (both S. African). Myxomatosis of rabbits (also 

 affecting dog and man, S. America). Agalasie con- 

 tagieuse de brebis. Infectious or pernicious anaemia of 

 the horse. Trachoma and a non-gonococcal urethritis 

 probably due to the same organism. Epithelioma con- 

 tagiosum of fowls and diphtheria of wood-pigeons, prob- 

 ably forms of the same disease. ' Farcin crytococcique.' 

 A disease (jaunisse) of silkworms. Mosaic disease of the 

 tobacco plant. Variola of carp. Disease of the lips of 

 barbel. Cyanolophia gallinarum, or chicken typhus, and 

 an allied disease affecting three species of thrush and the 

 starling in Italy. 



CHAPTER XX 



THE BACTERIOLOGY OF SEWAGE, SHELLFISH, 

 MEAT, SOIL, AIR, AND MILK 



The Bacteriology of Sewage. 



THE number of bacteria in ordinary town sewage varies 

 considerably, according to the age of the sewage, the 

 season, temperature, locality, and sometimes with the 

 nature of the waste liquors from factories. The number 

 often reaches several million per cubic centimetre. The 

 number of B. coli is given by Klein and Houston as from 

 90,000 to 2,000,000 per cubic centimetre, 100,000 being 

 an average; of B. Welchii, as from 100 to 1,000 per cubic 

 centimetre; and of streptococci, as at least 1,000 per c.c. 

 In addition to the above and those mentioned seriatim 

 at the end of the monograph, B. pyocyaneus, B. mycoides, 

 B. subflavus, B. cloacce, staphylococci, Cladothrix diclio- 

 toma, Beggiatoa alba, B. fluorescens stercolatus, B. fila- 

 mentosus, M. urece, and many others, are present. Re- 

 searches on the longevity of the typhoid bacillus in sewage 

 point to the fact that in crude sewage it cannot be expected 

 to survive longer than a fortnight, while the cholera vibrio, 

 on the other hand, was found by Houston to survive for 

 a month in one instance. 



