Organic matter 39.5 42.5 44.0 44.1 42.5 Nitrogen 47.5 33.9 46.7 32.4 40.1 Mineral substances 53.9 64.6 57.9 62.5 59.7 There is one fact to be borne in mind in estimating the manurial value of the dung of different animals--viz., that the quantity of dung voided by one animal is much greater than that voided by another. Thus the amount voided by the cow, for example, is much greater than that voided by the horse; so that, in this way, the inferior quality of the former is, to some extent, compensated for by its greater quantity. 2. _Urine._ The solid excreta possess, however, very much less manurial value than the urine. The former, as already stated, are undigested food-substances: any fertilising matters which they contain are such as have failed to be digested or absorbed into the animal system. The urine, on the other hand, contains those fertilising substances which have been digested. The amount of nitrogen and mineral matter, however, in the urine, does not represent necessarily the total amount of these substances. Thus, in the case of a growing or fattening animal, there is always a certain amount of these substances being absorbed to build up the animal tissue and put on flesh. In this respect it will be seen that the composition of urine will vary in the same way as that of the dung. In the case of the urine, however, there is a compensating influence to be taken into account. Urine is a waste product, and there is more waste in a young than in an adult animal. Another very important condition which determines the composition of urine is the nature of the food, especially the quantity of water drunk. This, of course, is obvious: the more water drunk, the poorer must the composition of the urine be. But here again, as in the case of the dung, this is largely compensated for by the total quantity voided--the more dilute the urine, the larger will its quantity be; so that the inferior quality is in this way made up for by its increased quantity. Keeping in mind, then, the fact we have just stated--viz., that the composition of urine will vary according to different conditions--we may obtain an approximate idea of what its composition is from the following results of analyses by Stoeckhardt. In 1000 parts the following quantities of _water_, _nitrogen_, _phosphoric acid_, and _alkalies_ were found to be present. From the following table it will be seen that the urine of swine (containing 97 per cent of water) is much poorer in nitrogen and alkalies than is the case with the urine of the sheep, horse, or cow.[134] While this is the case, the amount of phosphoric acid it contains is greater than that contained in the sheep's urine.