It appears, therefore, that the periodical revolution of the menstrual blood has great influence on delivery, and that it is the cause why the times of delivery in women vary so much more than in every other female who is not subject to the periodical evacuation, and which always bring forth at the same times. It also appears that this revolution, occasioned by the action of the menstrual blood, is not the sole cause of birth, but that the action of the fœtus itself contributes towards it, since there are instances of a child escaping from the womb after the death of the mother, which necessarily supposes an action proper and particular in itself.
The space of time which cows, sheep, and other animals go with young is always the same, and their deliveries are not attended with an hæmorrhage. May we not then conclude, that the blood voided by women after delivery is the menstrual blood, and that the human fœtus being born at such different terms, can only be by the actions of this blood on the matrix during every periodical revolution? It is natural to imagine, that if the females of viviparous animals had menses like women, their deliveries would be followed with an effusion of blood, and happen at different terms. The fœtuses of animals come into the world clothed with their membranes (and it seldom happens that the membranes are broken), and the waters flow before the delivery; whereas it is very rare a child is brought forth with its membranes entire. This seems to prove that the human fœtus makes more efforts than other animals to quit its prison; or that the matrix of a woman does not so naturally incline to the passage of the child, for it is the fœtus which tears its membranes, by the efforts it makes against the resistance it meets with at the orifice of the viscera.
All animals procure nutriment from vegetables, or other animals which feed upon vegetables; there is, therefore, one common matter to both, which serves for the nutrition and expansion bf every thing which lives or vegetates. This matter cannot perform them but by assimilating itself to each part of the animal or vegetable, and by intimately penetrating the texture and form of these parts, which I have called the internal mould. When this nutritive matter is more abundant than is necessary to nourish and expand the animal or vegetable, it is sent back from every part of the body, and deposited in one or more reservoirs, in the form of a liquor; this liquor contains all the molecules analogous to all parts of the body; and consequently all that is necessary for the reproduction of a young being, perfectly resembling the first. Commonly this nutritive matter does not become superabundant, in most kinds of animals, till they have acquired the greatest part of their growth; and it is for this reason that animals are not in a state of engendering before that time.
When this nutritive and productive matter, which is universally spread abroad, has passed through the internal mould of an animal or vegetable, and has found a proper matrix, it produces an animal or vegetable, of the same kind; but when it does not meet with a proper matrix, it produces organized beings different from animals and vegetables, as the moving and vegetating bodies seen in the seminal liquor of animals, in the infusion of the germ of plants, &c.
This productive matter is composed of organic particles, always active, the motion and action of which are fixed by the inanimate parts of matter in general, and particularly by oily and saline bodies, but as soon as they are disengaged from this foreign matter, they retake their action, and produce different kinds of vegetations and other animated, beings.
By the microscope, the effects of this productive matter may be perceived in the seminal liquors of animals of both sexes. The seed of the female viviparous animals is filtered through the glandular bodies which grow upon their testicles, and these glandular bodies contain a large quantity of seminal fluid in their internal cavities. Oviparous females have, as well as the viviparous, a seminal liquor, which is still more active than the viviparous. The seed of the female is in general like that of the male, when, they are both in a natural state: they decompose after the same manner, contain similar organic bodies, and they alike offer the same phenomena.
All animal or vegetable substances include a great quantity of this organic and productive matter. To perceive it, we need only separate the inanimate parts in which the active particles of this matter are engaged. And this is done by infusing animal or vegetable substances in water. The salts will dissolve, the oils separate, and the organic particles will be seen by their putting themselves in motion. They are in greater abundance in the seminal liquors than in any other parts, or rather, they are less entangled by the inanimate parts. In the beginning of this infusion, when the flesh is but slightly dissolved, the organic matter is seen under the form of moving bodies, which are almost as large as those of the seminal liquors: but, in proportion as the decomposition augments, these organnic particles diminish in size and increase in motion; and when the flesh is entirely decomposed, or corrupted, these same particles are exceedingly minute, and their motion exceedingly rapid. It is then that their matter may become a poison, like that of the tooth of a viper, wherein Mr. Mead perceived an infinite number of small pointed bodies, which he took for salts, although they are only these same organic particles in a state of great activity. The pus which issues from wounds abounds with little insects, and it may take such a degree of corruption as to become one of the most subtle poisons; for every time this active matter is exalted to a certain point, which may be known by the rapidity and minuteness of the moving bodies it contains, it will become a species of poison. It is the same with the poison of vegetables. The same matter which serves to feed us when in its natural state, will destroy us when corrupted. Spurred barley, for instance, throws the limbs of men and animals into a gangrene who feed on it. It is also evident by comparing the matter which adheres to our teeth, which is the residue of our food, with that from the teeth of a viper or mad dog, which is only the same matter too much exalted, and corrupted to the last degree.