BACTERIA IN FECES 249 
Escherich’s laboratory, was the first to determine the quantity of fecal 
bacteria by counting them in stained films. His experiments were 
carried out with normal infant’s stools. Coverglass preparations were 
made from fecal suspensions of known dilution and after being com- 
pletely dried were stained with freshly prepared aniline water fuchsin, 
then washed in water, air-dried, mounted in Canada balsam, and 
counted. The method was very much improved by Alex, Klein and 
Hehewerth. Klein had noticed that vegetative bacteria were more 
sensitive to disinfectants in a moist than a dry state, and this led him to 
believe that bacteria would also be stained more readily in a moist con- 
dition than after drying. Therefore he allowed the dye to act while 
the bacteria were suspended in a hquid and the coverglass preparation 
was made, dried, and fixed,.only after the bacteria were stained. Later 
the same investigator modified the method still further, using gelatin to 
fix the stained: bacteria to the coverglass. The aqueous solution of 
gelatin and the stained bacterial emulsion were put upon the cover- 
glass separately, then fixed and spread. When dry, the preparation 
was immediately mounted in Canada balsam without flaming. 
“The procedures as employed by MacNeal, Latzer and Kerr have 
been considerably modified. In the addition of the gelatin to the bac- 
terial suspension, in spreading the films, in selecting the fields to be 
counted, and in counting individuals, rather than groups, as units, the 
technic differs from Klein’s method. Of the 1: 100 suspension of the 
feces prepared as described above (p. 248), 23 c.c. are transferred to a 
clean, dry bottle, $ c.c. of melted nutrient gelatin and 2 c.c. of aniline 
water gentian violet added, and the whole thoroughly mixed and allowed 
to stand for three to five minutes. Then, by means of a platinum loop, 
the carrying capacity of which has been determined with great care, a 
loopful of the mixture, well shaken immediately before, is transferred 
to a clean, flamed 20 mm. square No. 1 coverglass and deposited near the 
center of the glass. Immediately another coverglass of the same size 
is accurately placed on top of the first so that the two glasses are in 
contact over about three-quarters of their surfaces and the sides evenly 
fitted together. As soon as the liquid has spread evenly between the two 
coverglasses, they are quickly slipped apart and allowed to dry. The 
technic here is the same as ordinarily used in the preparation of cover- 
glass blood films. If the preparation does not appear evenly spread 
the process is to be repeated with two more coverglasses until a satis- 
factory result is obtained. The films are next accurately measured by 
a millimeter rule and then, without further treatment, mounted in Can- 
ada balsam upon one slide so that one diagonal of each rectangular 
