9. The milk lasts a long time in those that have it, if they remain without sexual intercourse, and have proper food; and in sheep it lasts longer than in any other animals, for the sheep may be milked for eight months. Altogether the ruminating animals produce milk in greater abundance, and more fitted for making cheese. Around Torona the cows fail in their milk a few days before calving, but give milk all the rest of the time. In women dark-coloured milk is better for the children than that which is white; and black women are better nurses than white women. The most nutritious milk is that which contains the most cheese, but that which contains less cheese is better for infants.
Chapter XVII.
1. All sanguineous animals eject the spermatic fluid; the office it performs in generation, and how it is performed, will be treated of in another place. In proportion to his size man ejects more than other animals. This fluid, in animals covered with hair, is glutinous, in others it is not glutinous; in all it is white, so that Herodotus is mistaken when he says that the Ethiopians have black semen.[98] The semen comes out white and thick if it is healthy, but after ejection it becomes thin and black; it does not thicken with cold, but becomes thin and watery, both in colour and density. By heat it coagulates and thickens, and when it has been ejected for any time into the uterus, it comes out more thick, and sometimes dry and twisted together. That which is fruitful sinks in water, but the barren mixes with it. All that Ctesias said about the semen of the elephant is false.
BOOK THE FOURTH.
Chapter I.
1. We have hitherto treated of sanguineous animals, the parts possessed by all as well as those which are peculiar to each class, and of their heterogeneous and homogeneous, their external and internal parts. We are now about to treat of ex-sanguineous animals. There are many classes of these, first of all the mollusca.[99] These are ex-sanguineous animals, which have their fleshy parts external, and their hard parts internal, like sanguineous animals, as the whole tribe of cuttle-fish. Next the malacostraca, these are animals which have their hard parts external, and their interior parts soft and fleshy; their hard parts are rather liable to contusion than brittle, as the class of carabi and cancri.
2. Another class is that of the testacea. These are animals which have their internal parts fleshy, and their external parts hard, brittle, and fragile, but not liable to contusion. Snails and oysters are instances of this class.
3. The fourth class is that of insects, which includes many dissimilar forms. Insects are animals which, as their name signifies, are insected either in their lower or upper part, or in both; they have neither distinct flesh nor bone, but something between both, for their body is equally hard internally and externally. There are apterous insects, as the julus and scolopendra; and winged, as the bee, cockchafer, and wasp; and in some kinds there are both winged and apterous insects; ants, for example, are both winged and apterous, and so is the glowworm.
4. These are the parts of animals of the class mollusca (malacia); first the feet, as they are called, next to these the head, continuous with them; the third part is the abdomen, which contains the viscera. Some persons, speaking incorrectly, call this the head. The fins are placed in a circle round this abdomen. It happens in many of the malacia that the head is placed between the feet and the abdomen.