Section IV., 1906. [ 83 ] Trans. R. S. C. 



,1X. — The Distribuiion of Lactic Acid Bacteria in Curd and Cheese 



of the Cheddar Type, with Nine Illustrations from 



Photomicrographs. 



By F. C. Harrison, The Macdonald College, Ste. Anne de Bellevue, P.Q. 



(Communicated by Dr. James Fletcher, and read May 23rd, 1906.) 



Mme. Troili-Petersson and Gorini in 1903 and 1904 publislied 

 papers on the distribution of bacteria in Giiter and Grana cheese, and 

 employed and advocated histological methods of preparation and section 

 cutting for this purpose. Eecently Eodella again called attention to 

 the value of these direct microscopical preparations, and his paper on 

 account of the omission of Mme. T. Petersson's name in the historical 

 resume of the subject has already called forth replies regarding priority 

 of publication. Hence it seemed opportune to publish the results of 

 some work along the same lines as the above mentioned investigations, 

 but with Cheddar cheese of the Canadian type instead of the varieties 

 already investigated. 



Gorini in a footnote to his paper, referring to a previous investi- 

 gation published by Connell and myself stated that we suspected the 

 uneven distribution of bacteria in Cheddar cheese, without however, 

 giving any demonstration of it. This is correct so far as a direct ex- 

 amination of sections from cheese is concerned but we give in the paper 

 referred to several very good examples of the results of numerous quan- 

 titative analyses of Cheddar cheese which showed conclusively that the 

 bacteria were unevenly distributed not only in normal cheese but abnor- 

 mal cheese affected with the well known gaseous fermentation and wq 

 concluded the paragraph as follows : '' These examinations, which are 

 typical of many others which we have made show there is not an even 

 distribution of bacteria throughout the substance of a cheese, and it 

 would therefore, seem necessary to modify somewhat our methods of 

 analysis " a conclusion to which Gorini also arrives at in his paper 

 " Cette distribution irrégulière des bactéries augmente les causes d'erreur 

 dans l'analyse bactériologique quantitative du fromage." 



Thœe results have been confirmed by the histological investigation 

 of several cheese made according to the well-known Cheddar method. 



Methods of Imbedding. — Several methods were tried, of these, para- 

 tïin with oil of bergamot as a clearer gave the best results ; good results 

 were also obtamed by using chloroform as a clearer. Celloidin gave in- 

 ferior results, although the pieces of curd or cheese were passed through 

 2, 4, '6, 8, 10 and 12 per cent solutions of celloidin. 



