Now, although it is pretty generally known that musty corn and diseased potatoes form good feeding stuffs, it is not so patent whether or not the natural food of stock, such as hay and straw in a diseased state, is proper food for those animals. This question is worthy of consideration. Firstly, I shall describe the nature of the diseases which most frequently affect fodder; these are, "mildew" and "mould." These diseases are produced by the ravages of minute and very low forms of vegetable life, termed by the botanists _epiphytical fungi_. The mildew (_Puccinia graminis_) generally attacks the grasses when they are growing, and is more frequently met with on rich and heavily manured soils. In localities where heavy night-fogs and dews are of common occurrence, this pest often destroys whole crops. On the other hand, in light, sandy, and well-drained soils, and in warm and dry districts, the mildew is a rare visitant. The "blue mould" (_Aspergillis glaucus_) attacks hay and straw in the stack or rick, and without any regard to their origin--no matter whether they were the produce of the wettest or the dryest, the warmest or the coldest of soils. The chief condition in the existence of the blue mould is excessive moisture. If the hay or straw be too green and succulent when put up, or if rain get at them in the rick, the mould is very likely to make its appearance, and the well-known odor termed _musty_ will speedily be developed. Neither the mildew nor the mould can, strictly speaking, be regarded as parasites, such as, for example, the flax-dodder, which feeds upon the healthy juices of the plant to which it is attached. It appears to me that the tissues and juices of the fodder-plants decay _first_, and then the mould or the mildew appears and feeds upon the decomposing matter. Now, as these vegetables belong to a poisonous class of fungi, it is more than probable that they convert the decomposing substance of the straw or hay into unwholesome, if not poisonous matter; and it is not unlikely but that the disagreeable odor which they evolve is designed by nature as a sign to the lower animals not to partake of mouldy food. There is no doubt but that most animals will instinctively reject fodder in this state; and the question arises, ought this odour to be destroyed or disguised, in order to induce the animals to eat the damaged stuff? The experience of most feeders who have largely consumed mouldy provender is, that although cattle may be induced to eat it, they never thrive upon such stuff if it form a heavy item in their diet. The reason of this is obvious. The nitrogenous portion of the straw is that which is chiefly assimilated by the fungi. And as this constituent is the one which contributes to the formation of muscle, and is naturally extremely deficient in straw and hay--more particularly the former--it follows that the animals fed upon mouldy fodder cannot elaborate it into lean flesh (muscle).