Atu*. i, 1921 A Souring of Beef Caused by Bacillus megatherium 697 
source other than sour beef. For a determination of this problem both 
cultures obtained from the American Museum of Natural History were 
used for the inoculation of sterile specimens of raw beef. A third speci¬ 
men was inoculated with organism 1510-B. After 24 hours’ incubation 
it was found that the typical odor of sour beef had become pronounced 
in each of the samples inoculated. It was therefore concluded that B. 
megatherium is capable of producing the condition commonly known as 
sour beef. 
MICROSCOPIC APPEARANCE OF SOUR BEEF 
Several small pieces of artificially soured beef were prepared for sec¬ 
tioning by the paraffin method. Sections were made, mounted, and 
P 10 * 2 - A cross section of beef muscle inoculated with organism 1510-B, stained by the Gram-Weigert 
method to show bacteria. Pen-and-ink drawing from microscope with aid of camera lucida. 
stained by the Gram-Weigert method to show bacteria. Figure 2 is a 
reproduction of a pen-and-ink drawing made with camera lucida from one 
of the sections as seen under the microscope. The organisms are seen in 
large numbers on the exterior surface of the section, a fact which may be 
accounted for by the aerobic nature of the organisms. As they pene¬ 
trated into the interior of the meat, growing between the muscle fibers, 
their multiplication was greatly inhibited by the anaerobic condition 
of the interior of the tissue, and yet a few persevering organisms may be 
seen to have penetrated well into the tissue. 
