OYSTERS 463 



Extract.- 



1. Introduce various quantities of the bouillon ex- 

 tract into the stomachs of several rats, mice and guinea- 

 pigs repeatedly over a period of two or three days by 

 the intragastric method of inoculation (see page 367) 

 and observe the result. Guinea-pigs and mice are very 

 susceptible to infection by B. botulinus by this method; 

 rabbits less so. 



2. Inoculate rats, mice, and guinea-pigs subcuta- 

 neously into deep pockets, and intraperitoneally with 

 various quantities of the bouillon extract, and observe 

 the result. 



3. Filter some of the extract through a Chamberland 

 candle and incubate the filtrate to determine the 

 presence of soluble toxins. 



4. If any of the animals succumb to either of these 

 methods of inoculation, make careful post-mortem 

 examinations and endeavour to isolate the pathogenic 

 organisms. 



THE EXAMINATION OF OYSTERS AND OTHER SHELLFISH. 



On opening the shell of an oyster a certain amount 

 of fluid termed "liquor" is found to be present. This 

 varies in amount from a drop to many cubic centi- 

 metres (o.i c.c. to 10 c.c.) in the latter case the bulk 

 of the fluid is probably the last quantum of water in- 

 gested by the bivalve before closing its shell. In 

 order to obtain a working average of the bacterio- 

 logical flora of a sample, ten oysters should be taken 

 and the body, gastric juice and liquor should be 

 thoroughly mixed before examination. The examina- 

 tion, as in dealing with other food stuffs, is directed to 

 the search for members of the Coli-typhoid group, 

 sewage streptococci and perhaps also B. enteritidis 

 sporogenes. 



