No greater contrast could be imagined than that which separates such works from those which are the production of our modern writers on the same subject. Nor does this difference depend, as one might suppose, on the fact that a wider field of observation is open to us, and more adequate collections of facts are at our disposal. Rather is it the case that between ancients and moderns, between the eastern and western world, there is an entirely different understanding of the whole subject. A different principle of arrangement is at work, and results in the wide diversity of manner which strikes us as soon as we open the _De Animalibus_ or the _Abbreviatio_. We find ourselves in the presence of a system of ideas, more or less abstract, which a wealth of facts derived from keen and wide observation of the world of nature is employed to illustrate. There is a finer division than with us. The unit in these works is not the species nor even the individual, but some single part or passion. This the author follows through all he knew of the multitudinous maze of nature, comparing and discerning and recording with a _bizarrerie_ which comes to resemble nothing so much as the fantastic dance of form and colour in a kaleidoscope. ‘Birds,’ says Avicenna,[104] ‘have a way of life that is peculiar to themselves. Those that are long-necked drink by the mouth, then lift their head till the water runs down their neck. The reason of this is that their neck is long and narrow, so that they cannot satisfy their thirst by putting beak in water and straightway drinking. There is, however, a great difference between different birds in their way of drinking, and the mountain hog loveth roots to which his tusk helpeth, wherewith he turneth up the ground and breaketh out the roots. Six days or thereabout are proper for his fattening, wherein he drinketh not for three, and there are some who feed their hogs and yet will not water them for perchance seven days on end. And in their fattening all animals are helped by moderate and gentle exercise, save the hog, who fatteneth lying in the mud, and that mightily, for thereby his pores are shut upon him so that he loseth nothing by evaporation. And the hog will fight with the wolf, and that is his nature, and cows fatten on every windy thing, such as vetches, beans, and barley, and if their horns be anointed with soft wax, straightway, even while still upon the living animal, they become soft, and if the horns of ox or cow be anointed with marrow, oil, or pitch, this easeth them of the pain in their feet after a journey.’