As to the growth of the fœtus in the uterus, Empedokles held that it was enveloped in a membrane, and that its formation began on the thirty-sixth day and was completed on the forty-ninth. The heart was formed first, the nails and such things last. Respiration did not begin till the time of birth, when the fluids round the fœtus were withdrawn. Birth took place in the ninth or seventh month, because the day had been originally nine months long, and afterwards seven. Milk arises on the tenth day of the eighth month (fr. 68).[629] Death was the final separation by Strife of the fire and earth in the body, each of which had all along been striving to “reach its own kind.” Sleep was a temporary separation to a certain extent of the fiery element.[630] At death the animal is resolved into its elements, which perhaps enter into fresh combinations, perhaps become permanently united with “their own kind.” There can be no question here of an immortal soul. Even in life, we may see the attraction of like to like operating in animals just as it did in the upward and downward growth of plants. Hair is the same thing as foliage (fr. 82); and, generally speaking, the fiery part of animals tends upwards and the earthy part downwards, though there are exceptions, as may be seen in the case of certain shell-fish (fr. 76), where the earthy part is above. These exceptions are only possible because there is still a great deal of Love in the world. We also see the attraction of like for like in the different habits of the various species of animals. Those that have most fire in them fly up into the air; those in which earth preponderates take to the earth, as did the dog which always sat upon a tile.[631] Aquatic animals are those in which water predominates. This does not, however, apply to fishes, which are very fiery, and take to the water to cool themselves.[632] Footnote 629: Aet. v. 15, 3; 21, 1 (_Dox._ p. 190). Footnote 630: Aet. v. 25, 4 (_Dox._ p. 437). Footnote 631: Aet. v. 19, 5 (_Dox._ p. 431). Cf. _Eth. Eud._ Η, 1. 1235 a 11. Footnote 632: Arist. _de Respir._ 14. 477 a 32; Theophr. _de causis plant._ i. 21. Empedokles paid great attention to the subject of respiration, and his very ingenious explanation of it has been preserved in a continuous form (fr. 100). We breathe, he held, through all the pores of the skin, not merely through the organs of respiration. The cause of the alternate inspiration and expiration of the breath was the movement of the blood from the heart to the surface of the body and back again, which was explained by the _klepsydra_.