620 A MANUAL OF BACTERIOLOGY 



of the narrow end down to within \ in. of the deposit are sucked out 

 with a fine glass pipette, the upper part of the tube is wiped clean 

 and the tube is then filled to the 10 c.c. mark with salt solution. 

 The tube, having been violently shaken till all the deposit is dis- 

 tributed through the liquid, is then rotated for four minutes, and 

 the liquid down to within | in. of the deposit again removed. In 

 the case of small deposits, two to three drops of saturated aqueous 

 solution of methylene-blue are added, and the deposit is stirred 

 up by blowing through a fine glass capillary pipette (which is 

 afterwards used for filling the counting chamber). After fifteen 

 minutes, water is added to the 1 c.c. mark, and counting done in 

 the usual way with a Thoma-Zeiss blood counter. Counting should 

 not be restricted to the ruled spaces, but the field should be so ar- 

 ranged that a definite number of squares is included, and fields are 

 counted all over the chamber. At least two different preparations 

 should be made of the same deposit for counting. 



FOOD PoisoNiNG. 1 Apart from the presence of the ordinary 

 poisons, food may be poisonous on eating (a) naturally, e.g. certain 

 fish, (6) from the results of the activity of micro-organisms with 

 the formation of toxic products, the ordinary " ptomine poisoning " 

 (see p. 38), in which case the poison is pre-formed and is ingested, 

 (c) from infection with certain organisms, particularly B. enteritidis, 

 which generally induce gastro-enteritis. In the last named, symp- 

 toms do not usually ensue until a lapse of twelve to forty-eight 

 hours after the consumption of the food. Mayer and Mandel 

 describe an outbreak following the consumption of broiled fish, 

 in which B. proteus was isolated from the stools and was agglutinated 

 by the patients' serum. 



Meat is not likely to convey any infective disease with the excep- 

 tion of tuberculosis and anthrax. It may be examined by cultures 

 and plate cultivations, and by inoculation and feeding experiments. 

 Tinned meats, etc., frequently contain sporing organisms of the 

 B. subtilis and mesentericus groups. They may be examined by 

 aerobic and anaerobic cultures, and by feeding mice. Poisonous 

 ptomines are occasionally present. The B. enteritidis occurs in 

 meat, and causes a form of poisoning (see p. 371 ). 2 In certain 

 intoxications due to bad meat, known as " botulism," Van Ermengen 

 isolated the B. botulinus (see p. 427). 



Bread. Troitzki states that new bread contains no micro- 

 organisms, but Waldo and Walsh found that such organisms as 

 the comma bacillus are not destroyed by passing through the ordeal 



1 See Savage, Hep. to the LOG. Gov. Board, No. 77, 1913. 



2 See Savage, Eep. Med. Off. Loc. Gov. Board for 1909-10, p. 446. 



