498 SUMMARY OF CURRENT RESEARCHES RELATING TO 



no record of tubercle occurring naturally in salt-water fish. From a 

 pure culture of a virulent strain of the B. tuberculosis of fresh-water 

 fish, the author prepared an emulsion, and with this inoculated a 

 number of fish belonging principally to the genera Sparus and Serranus. 

 Of these, two died : the first 1 month, the second 7 months, after injec- 

 tion. In the latter he found tuberculosis of the swimming-bladder, in 

 the former the disease was almost entirely confined to the site of inocu- 

 lation. Thus, in neither case was there generalised tuberculosis. Ex- 

 periments with human and avian tubercle are still in progress. 



Scientific Cheesemaking.*— Under the title of Technique frontager e, 

 P. Maze considers the theoretical basis of the scientific manufacture of 

 cheese, and the practical application of principles so established. Cheese 

 is defined as consisting merely of the insoluble extract of milk, somewhat 

 altered, and deprived, as completely as possible, of milk sugar. For this 

 purpose it is undesirable to obtain complete solution of casein. It is 

 thus necessary, in the first place, to prevent the interference of pepton- 

 ising ferments, and secondly, to secure the operation of useful ferments 

 which act upon the milk sugar, but do not attack nitrogenous matter or 

 fat. This is effected by getting the proper balance between antagonistic 

 microbic ferments. 



The fermenting organisms fall into three classes : the lactic ferments, 

 the ferments of combustion, and the alkaline ferments. The conven- 

 tional standard of efficiency for the first class of organisms is that they 

 should produce 12 grm. of lactic acid per litre of milk. The acidifying 

 power is directly in proportion to the power of multiplication. Many 

 bacteria which produce lactic acid are unsuitable because they also give 

 rise to acetic acid, and this except in the merest traces is undesirable. 

 The morphological characters of this class vary, especially in the size of 

 the individuals ; as ovoid cocco-bacilli, single or paired, they are found 

 in milk ; in chains, they may appear in broth, but in milk this appear- 

 ance indicates an undesirable type of fermenter. The characters of 

 colonies upon solid media afford an important means of distinguishing- 

 different species. All lactic fermenters produce a certain degree of solu- 

 tion of casein in an acid medium. If the clot becomes alkaline, this 

 solution proceeds further. It is undesirable that this action should ad- 

 vance to a further break-up of nitrogenous material, for the products of 

 such action would impart a disagreeable flavour to the cheese. 



A growth of mould appears upon the surface of the material after 

 two days. These moulds produce combustion ferments which destroy 

 milk sugar and lactic acid, thus arresting the activity of the lactic fer- 

 ments. The cheese becomes alkaline and solution of casein begins. 

 These moulds consist of various species of Oidium, Mgcoderma, and Peni- 

 cillium. Penicillium is the most active in the attack upon sugar, but 

 Oidium (particularly Oidium camemberti) is most desirable in that it 

 spares casein. 



The alkaline ferments are produced by certain small non-motile 

 aerobic bacilli, the " ferments de rouge." These complete the destruction 

 of sugar and attack the lower nitrogenous products. There are a great 

 number of species of these organisms, possessing different degrees of 



* Aim. Inst. Pasteur, xxiv. (1910) pp. 395-428. 



