198 UNIVERSITY OF WISCONSIN STUDIES 
should certainly be kept out of ice cream plants by every 
possible method. It now seems evident also that a negative 
Widal is by no means definite proof that a certain individual 
is not a carrier. An epidemic in Brooklyn in 1914”? was not 
traced to its source, and in 1915 another epidemic in the 
same section led to stool examinations of the employees of an 
ice cream plant supplying most of the ice cream, with the re- 
sult that a man who had been working in the factory in 1914 
was found to be a carrier. A typhoid epidemic in California** 
was found to have been due to ice cream made by a woman 
who had had typhoid 17 years before and who gave only 
a partial Widal. This same ice cream also caused poisoning 
in the persons consuming it and all but two of the persons 
poisoned developed typhoid. A portion of the ingredients 
was heated, then cooled and added to whipped cream, after 
which the mix was allowed to stand from 6:30 until 1:00 
o’cloek without ice, before being made into ice cream. 
The presence of organisms producing disease in non-epi- 
demic form is very likely to occur unless proper care and 
handling are followed. 
If pathogenic organisms are present in ice cream, the low 
temperatures to which they are subjected during the harden- 
ing and holding process cannot be depended on to destroy 
them. While there will likely be a falling off in the numbers 
of living cells, low temperature cannot be counted on to make 
the product safe. At the Iowa Agricultural Experiment 
Station,?* ice cream artificially infected with the tubercle 
bacillus was found capable of producing tuberculosis in guinea 
pigs after one month, which is as long as the tests were made, 
this period being considerably longer than ice cream is likely 
to be held under practical conditions. 
2 Letter from New York City Health Dept. 
2 yr, Am, Med. Assn., April 21, 1917. 
* Unpublished data. 
