The disease, however, of all others which owes its inception to cooked food is that terrible autumn epidemic, diarrhoea. Vincent says: "It is essential for the development of the disease that the characteristic properties of the natural food of the infant should have been destroyed by heat, by preservatives, or some other means." Milk left to itself soon curdles by virtue of the lactose being converted into lactic acid by the lactic acid bacillus. Such milk creates digestive disturbances in infants, but this differs from zymotic enteritis in the absence of the toxaemia which is the characteristic and fatal feature of the disease. Raw milk which has soured is easily detected, and need not be used, but even if so, the lactic acid bacillus prevents the development of changes of a poisonous character. The cause of zymotic enteritis, he declares, is the toxins produced by the ordinary organisms of putrefaction, which can only grow in milk in which the lactic acid bacillus has been destroyed by the application of heat or some other agency. To prevent the disease, therefore, he insists on a supply of pure raw milk being placed within the reach of every family.

It is well known that boiled milk is much more constipating than fresh milk, and it may be that this is due to the destruction of its contained lactic acid bacillus. This is hardly likely, however, as with many people curdled milk is quite as constipating, and it is probable we must look to some change in the caseinogen, or its large content of calcium, to account for the constipating qualities. There is no evidence that boiling in any way impairs the nutritive qualities of milk or any other food, although cooking produces profound changes in their character. A ripe raw apple possesses a sweetish flavour with just a sufficient suspicion of acidity to commend it to the taste, but the same apple stewed or cooked becomes so acid that it may require to be deluged with sugar before it can be eaten. This is a peculiarity of most fruits, that they taste much better raw than cooked, and may be an indication that the natural method is to eat them in the raw condition.

It is also certain that they are much more easily digested in that condition by the majority of people, and it has been asserted that they contain enzymes in the form of oxidases and diastases from which the body may derive benefit and which are destroyed in the process of cooking. If this could only be demonstrated, it would be an infinitely more satisfactory argument in favour of raw food than the frequent reiteration of the elusive element of vitality, a property which it is absolutely impossible to define. The increase of acidity suggests that some volatile alkaline ingredient has been driven off by the application of heat, which would serve to neutralise the harmful acid ingredients or render them more tolerable to the body juices. It may be, indeed, that some valuable natural chemical salt is decomposed, and that in this way the body is being robbed of some essential nutrient.

Raw fruit is therefore more appetising than cooked fruit. It does not follow, however, that raw flesh is in the same position, although the raw-fooder, and with him the flesh-feeder, would assert that the development of agreeable flavours in meat by the process of cooking is an unnatural pandering to a depraved appetite. Cooked meat is said to take longer time to digest than raw meat, but this is quite inexplicable on the hypothesis that agreeable flavours which encourage a flow of gastric and other juices are developed by the cooking process. In any case it is a certainty that cooked meat is much more easily masticated than similar meat in a raw state, and this is obviously advantageous when we reflect that in the case of meat the only function subserved by mastication is that of comminution, as it contains no element upon which the diastatic power of the saliva can be exerted. It is no argument against the use of flesh as a food to say that it requires cooking, for custom and instinct alike demand that most fleshless foods be rendered agreeable and more digestive by the process of cooking.