INVESTIGATIONS OF ACID ORGANISMS OF MILK. —* 69: 
examination of the udders of cows. ‘The first series, com- 
prising Experiments 1-10, was carried out during 1900. ‘The 
second, comprising Experiments 11-15, was conducted a year 
later. The third series was also carried out in 1901. The 
investigations were made by the: writer while an assistant in 
the bacteriological laboratory of the Connecticut Hospital for 
the Insane. 
Subjects and conditions.—The herd which was used in the 
experiments consisted of perfectly healthy cows, typical in 
every respect of the best kept cows of the farmer. It con- 
sisted of nearly a hundred cows, mostly of the Holstein breed. 
The herd was owned by the Connecticut Hospital for the 
Insane, and the success of the experiments was in large degree 
due to the excellent condition of this herd and its surround- 
ings. ‘The barn was perfectly ventilated and slightly warmed 
by steam. ‘The heat from the steam produced a slight upward 
current of air which passed through a large number of win- 
dows opening in the roof directly above the stalls, and thus 
established a complete ventilation. The floors were of hard 
cement and were cleaned four or five times each day. The 
cows were groomed morning and night, and during the warm 
summer months were sprayed with a disinfectant. All utensils 
of the dairy were thoroughly scalded and kept well polished. 
The cows when not feeding in the pasture were given ensilage. 
In short, the conditions were those of a model dairy. 
Preparation of media.—In the experiments a variety of cul- 
ture media were tested, some of them being those commonly 
used in bacteriological laboratories, while others were especially 
devised for the purpose. Some experiments were made with 
media made from milk, but it was found that the litmus-milk- 
sugar gelatin, which has been used by EHsten and Conn in their 
experiments, was most satisfactory, and eventually all other 
media were discarded and the experiments detailed below were 
all performed with this medium. 
FIRST SERIES OF EXPERIMENTS. 
Experiment No. r.—The object of the first experiment was 
to determine whether milk as freshly drawn from the cow 
contains acid organisms or whether the acid organisms area 
6 
