94 Journal of Agricultural Research voi. xxii. no. 2 



Troili- Peterson {11), in discussing tlie bacterial flora of Swedish 

 "Giiterkase," mentions the microscopic examination of cheese as a 

 control for the cultural procedure but does not give the technical details. 

 She presents photomicrographs of cheese sections and states that some of 

 the preparations were stained in methylene blue and that a few were 

 examined unstained. 



Gorini (j), in studying the distribution of the bacteria in Grana cheese, 

 presents the details of a method by which he prepared sections for 

 microscopic examination. In his procedure he fixed and dehydrated 

 samples of cheese by passing them through a series of alcohols of increasing 

 concentrations until a strength of 95 per cent was reached. The usual 

 histological methods of sectioning were followed, and the sections were 

 stained in an aqueous solution of methylene blue. 



In the following year Rodella (9) reported a method used in his labo- 

 ratory for preparing sections used in the direct examination of cheese 

 samples. With his technic the samples were dehydrated and fixed by a 

 method similar to that of Gorini and sectioned in the usual way. He 

 found, however, that carbol-thionin gave better results as a stain than 

 did methylene blue. 



Harrison (<5) outlined in detail a method for embedding and sectioning 

 cheese which is similar to the common histological method, but like his 

 predecessors he made no estimate of the number of bacteria present. 



During the year in which Rodella (9) presented his paper, Troili- 

 Peterson {12) and Gorini (4) published notes discussing the question of 

 priority raised by the practically simultaneous publication of their 

 papers. It appears that the methods followed by Trioli- Peterson were 

 similar to those of Gorini, but that she did not feel the necessity of pre- 

 senting the technical details because of the universal knowledge of the 

 common embedding methods. 



No results have been obtained in any of this work that permit a com- 

 parison between counts made by the plate method, so commonly used 

 in floral studies of cheese, and counts made by direct microscopic examina- 

 tion. Following the method outlined below, comparatively accurate 

 counts have been made by the direct method, and the number of the 

 different types of bacteria have been determined as they actually exist 

 in the cheese mass. 



TECHNIC 



EMBEDDING AND SECTIONING 



The samples of cheese were embedded by the usual histological technic 

 and sectioned with a Minot rotary microtome. In sectioning, the micro- 

 tome was so adjusted as to give sections 5 ^i thick. The sections were 

 stained by the Gram method and with an aqueous solution of methylene 

 blue. 



