The Worlt of Aciditif in Glieese-making. 
285 
in some cases be even less) tliau that of the untreated milk ; 
whilst the whej^ of the milk which was alkalised may be the 
most acid of all. But, notwithstanding the curious change 
which has thus taken place in the relations of the three samples 
of whey in this respect, those of the curds are not appai'ently 
altered. The curd of the alkaline milk is still soft and incoherent, 
although its whey is now of so high a degree of acidity, whilst 
that of the acidified milk is still tougher than that of the others 
although they have overtaken it in the race of acidity. 
This somewhat pai-adoxical fact shows conclusively that it is 
at the earliest stage of its formation that the permanent character 
of the curd is impressed upon it, and that it is at this stage also 
that acidity produces its special effect in modifying the peculiar 
action of rennet. It is true that the defect arising from deficiency 
of acidity at the renneting stage may to some extent be corrected 
by encouraging the development of acidity at a later one (that 
of draining, after the whey has been removed) ; but the error 
caused by excess of acidity at starting can never be effectually 
rectified afterwards, and the only remedy for it is to push on the 
ripening and marketing of the cheese as rapidly as possible. 
In addition to the effect which acidity thus produces in 
modifying the tenacity of the curd developed by the special 
action of rennet, it exercises two other actions in cheese-making 
which are of considerable importance. 
In the experiment described above we have indicated the 
effect of insufficient acidity as it may be shown in sound milk 
the natural acidity of which has been artificially neutralised by 
the addition to it of a certain amount of alkali. But this con- 
dition of deficient acidity may, under certain circumstances, be 
met Avith naturally in milk, and when this is the case its effect in 
cheese-making is most pernicious. And the reason is simply this : 
the absence of a certain degree of aciditj" — still more the presence 
of marked alkalinity — in fresh milk is in the great majority of 
cases, if not in all cases, a symptom of disease, either local or 
general, in the cow from which the milk has been taken, for it is 
caused by excess of alkaline phosphates in the milk, and this is, in 
its turn, due to excessive tissue-waste. Now, alkalinity in a highly 
organised fluid like milk is a most favourable condition for the 
development in it of the germs which bring about putrefactive 
decomposition, even if those germs are not already present in it 
as the result of disease.^ Hence such milk exhibits, when treated 
with rennet, during the curding stage, unmistakable evidence of 
' Mnch light has been thrown on this .subject by the researches of 
Duclaux, a full account of which will be found in the monograph Le Lait 
(Paris, 1887 : J. B. Baillierc et fils. Pp. 336. 3fr. 50c.). 
