288 



BACILLI OF THE TYPHOID GROUP 



typhoid bacilli are found here. Rub up the loopful of bacteria in a 

 clean watch-glass with a sufficient quantity of distilled water to make 

 an even milky but not very concentrated emulsion. Place a small 

 drop of this emulsion on a clean cover-glass, add another drop of 

 water with the platinum loop, and again mix thoroughly until an 

 even, homogeneous emulsion is obtained. Place the cover-glass over 

 a concave slide, around the concavity of which vaselin has been 

 painted. Examine this hanging drop with oil-immersion magnification 

 to ascertain that the typhoid bacilli are lively, motile, and not clumped. 

 2. Prepare "another cover-glass by placing on it a small drop of 

 the typhoid bacilli emulsion in the watch-glass. 



FIG. 143 



FIG. 144 



Typhoid bacilli from nutrient gelatin. 

 X 1100. (Park.) 



Gruber-Widal reaction. Bacilli gathered into 

 one large and two small clumps, the few isolated 

 bacteria being motionless or almost so. 



3. Mix a small drop of dried blood on the cover-glass with about 

 10 to 20 drops of distilled water, which are added with the platinum 

 loop. Then rub up well with the dried blood, which, of course, is now 

 dissolved out by the water. This mixing is done directly on the slide 

 on which the blood was collected and allowed to dry. 



4. Add to the emulsion on the second cover-glass, with platinum 

 loop, a small drop of the dilute blood, mix well, and place cover-glass 

 on a concave slide. 



There are now two hanging-drop preparations: the first one is 

 simply an emulsion of young typhoid bacilli in distilled water, which 

 serves as a control for the second, which contains bacilli and distilled 

 water together with diluted blood from the suscepted cases of typhoid 

 fever. If this case is indeed one of typhoid fever it will be noted 

 after fifteen to thirty minutes (sometimes even earlier) that the typhoid 

 bacilli mixed with the dilute blood lose their motility, become glued 

 to each other in little masses, and finally become indistinct, while 



