POISONOirs FOODS. 507 



g-iutination, the test should be repeated with higher dilu- 

 tions. Thus, 1 drop of 1:10 added to 10 drops of water 

 will give 1:100. 



Some workers prefer to make the dilutions with a 

 ybung bouillon culture (6 to 8 hours at 37°) of the Eberth 

 bacillus. This is intended to obviate the possible error of 

 mistaking the clumps of bacteria as occasionally found in 

 agar cultures for the real agglutinated masses. 



■ The reaction is applicable to dried blood and, indeed, this is per- 

 haps the most convenient way of sending^the material for an examin- 

 ation. The blood is allowed to fall, drop by drop, on different portions 

 of a piece of fllter-paper. When the blood has dried perfectly the 

 paper may be folded and mailed. The blood-stained circles, each repre- 

 senting' one drop pf blood, are cut out and placed in dishes containing 

 10, 20, 30, etc. , drops of water, respectively. The solution of the blood 

 constituen-ts is facilitated by crushing the bit of paper with a glass rod. 

 Hanging-drops are then prepared in the manner indicated above. 



According to Johnston and MacTaggart pseudo-reactions are 

 characterized by rapid clumping without the corresponding loss of 

 motion Which is so characteristic of the true reaction. After a few 

 hours these clumps tend to break up. These pseudo-reactions can be 

 avoided by using an attenuated culture which is transplanted at in- 

 tervalaof about a month and grown at the room temperature. From 

 such stock cultures a bouillon culture is made and developed at 37° 

 for 24 ipurs. This is then employed. By using such attenuated cul- 

 tures the authors do not consider it necessary to make dilution tests. 

 A large drop of water is placed on the blood stain and allowed to 

 stand for a minute or two. A loopf ul of the solution thus obtained is 

 taken from the top of the drop and mixed with a loopful of the 

 bouillon culture. The reaction is usually given in this method in 

 ahout 15 minutes. 



Poisonous Foods. 



The examination of food which is suspected to be the 

 cause of illness is frequently demanded. Before the devel- 

 opment of bacteriology these cases of poisoning were 

 usually believed to be due to metallic poisons which were 

 introduced, 'accidentally or otherwise, into the food. The 



