and the nutriment proceed from the mother, and the plastic virtue from the father ; or rather a certain contagion im- mitted during intercourse, or produced and received from him, which in the body of the hen, or in the eggs, either perma- nently excites the matter of the eggs, or attracts nourishment from the female, and concocts and distributes it first for the growth of the eggs, and then for the production of the chicks ; finally, whether from the male proceeds all that has reference to form and life and fecundity, from the female, again, all that is of matter, constitution, place, and nourishment ? For among animals where the sexes are distinct, matters are so arranged, that since the female alone is inadequate to engender an em- bryo and to nourish and protect the young, a male is associated with her by nature, as the superior and more worthy progenitor, as the consort of her labour, and the means of supplying her deficiencies; in the case of the hen, of correcting by his contagion the inferiority of the hypenemic eggs which she produces, and so rendering them prolific. For as the pullet, engendered of an egg, is indebted to that egg for his body, vitality, and principal or generative part, so and in like manner does the egg receive all that is in it from the female, the female in her turn being dependent on the male for her fecundity which is conferred in coition.
And here we have an opportunity of inquiring, whether the male be the first and principal cause of the generation of the offspring ; or whether the male along with the female are the mediate and instrumental causes of nature itself, or of the first and supreme generator? And such an inquiry is both be- coming and necessary, for perfect science of every kind de- pends on a knowledge of causes. To the full understanding of generation, therefore, it is incumbent on us to mount from the final to the first and supreme efficient cause, and to hold each and every cause in especial regard.
We shall have occasion to define that which is the first and supreme efficient cause of the chick in ovo by and by, when we treat of that which constitutes the efficient cause [of gene- ration] among animals in general. Here, meantime, we shall see what its nature may be.
. The first condition, then, of the primary efficient cause of generation, properly so called, is, as we have said, that it be
