30 BULLETIN 433, U. S. DEPARTMENT OP AGRICULTURE. 



Room No. 2 : 6 bj^ 6 feet by 7 feet 4 inches Mgh, witb overliead bunker, closed 

 brine-coil system of refrigeration, forced circulation of air, and automatic 

 temperature control. This room was used as a place in which to cut up the 

 meat and prepare it for analysis, and for certain laboratory work which 

 required a low temperature. 



As soon as the beef was received from the packing house it was 

 placed in cold-storage room No. 1, unwrapped, weighed, and hung 

 up. During each storage experiment the temperature of the room 

 was recorded continuously by means of a recording thermometer. It 

 was the aim to keep the temperature at 32° to 36° F., but the exact 

 temperature range will be stated in connection with each experiment. 

 The humidity of the room was determined once each week by means 

 of a sling hygrometer, and observations as to the condition of the 

 meat were made at the same time. Each quarter of beef was weighed 

 at the end of the period of storage. 



BACTERIOLOGICAL AND HISTOLOGICAL STUDIES. 



In the bacteriological study of the carcasses the two main ques- 

 tions investigated were: (1) Whether bacteria are present in the 

 muscular tissues of beef animals which have been passed as normal 

 after careful ante-mortem and post-mortem examination, and (2) 

 whether the bacteria and molds which grow on the surfaces of cold- 

 stored meats penetrate the meats to any marked degree during vary- 

 ing periods of storage. 



With regard to the second question, there are two methods by 

 which the surface bacteria might penetrate the meats, namely, (1) 

 by direct growth or extension into the muscular tissues or (2) by 

 growth along the tendinous sheaths or connective-tissue elements be- 

 tween the muscle groups. In the present study the latter method 

 was not investigated and the cultures were always made from the 

 muscular tissue, avoiding the connective-tissue elements, the idea 

 being to determine whether the bacteria actually penetrate the mus- 

 cular tissue. 



In examining the quarters bacteriologically the following pro- 

 cedure was adopted : A slice or section from 3 to 4 inches thick was 

 cut from the upper portion of the round. From this slice a rectan- 

 gular block extending from the outer surface to the botie was cut, 

 as indicated by the dotted line in the diagram (fig. 1). This block, 

 which measured about 4| by 8 inches and weighed from 6 to 8 

 pounds, was first immersed in actively boiling water for three 

 minutes, next in bichlorid solution (0.6 per cent) for five minutes, 

 and was then wrapped in sterile gauze which had been wrung out 

 in the bichlorid solution. This was done in order to sterilize the 

 surface of the meat and to prevent the growth and possible penetra- 

 tion of bacteria from the outside, pending the taking of cultures. 



