86 ROYAL SOCIETY OF CANADA 



micro-pliotograpli of lower magnification shews the enormous number of 

 bacteria present and clumps, or aggregations of bacteria of various sizes. 



8. Cheese tivo days old. — Little change has occurred in either the 

 texture or numbers of bacteria present, since the salting stage. Fig. 8 

 shews a large mass of bacteria around an open space in the cheese and 

 Pig. 9 of lower magnification gives a good idea of the distribution of the 

 bacteria in the cheese. 



The starter or pure culture used in the manufacture of this cheese, 

 was a lactic acid bacillus which grew in small chains, and it could be 

 quite readily recognized in microscopical preparations of either butter or 

 cheese, made from cream or milk in which it had been introduced, as 

 the lactic acid bacteria naturally present did not form these characteristio 

 chains. It was always easy in this particular dairy to distinguish the 

 dairy products in which it had been used from those made from natural 

 ripening. 



Conclusions : — 



1. The paraffin imbedding method, as already outlined gives ex- 

 cellent results in the preparation of curd or cheese for microscopical 

 examination. 



2. (jram's method of staining, with eosin as a contrast stain 

 brings out the lactic acid bacferia, yeasts, and torulas or all organisms 

 which are known to accept this stain and hence this method of coloration 

 has some diagnostic value. 



3. Organisms in curd or cheese which do not accept Gram's stain 

 may be demonstrated by the use of Bismarck brown. 



4. Practically all bacteria are stained if amyl alcohol is used for 

 decolorising or dehydrating. 



5. The lactic acid bacteria increase very rapidly in numbers from 

 the time the rennet is added to the milk until the time of salting. 



6. The increase in numbers of these bacteria from the time of 

 salting until the cheese is a day or two old is not very pronounced. 

 Comparison, however, is difficult on account of the huge numbers 

 present. 



7. The lactic acdd bacteria have a tendency to form clumps or 

 colonies of various sizes. Over a thousand cells have been counted in a 

 single clump or colony. 



8. The results confirm the quantitative analysis of curd and cheese 

 by the plate method, and the amount of acid developed in the whey 

 during the progress of making is an indication of the extraordinary mul- 

 tiplication of the lactic acid bacteria present in the curd. 



