697. So soon as the connection of body and mind is abolished, and, consequently, proper animal life ended, all these animal operations cease to be sentient actions, although, in consequence of the maintenance of mere animal life, they may still be produced by the vis nervosa only. (Part II, Chap. IV, sect. i.) They may be produced, however, in virtue of the natural coordination of the forces of the mind and the nerves, by both acting at the same time in parallel subordination. (Part II, Chap. IV, sect. ii, iii.) But as the animal-sentient forces are subordinate to the primary vital forces towards the close of mere animal life, the animal functions cannot be produced by the former, but all proper animal life must cease at the same time (640).

698. Thus then, in the perfect condition of the animal, all its animal forces are both subordinate and co-ordinate in the most wonderful manner; whence in the system of all the forces of the complete animal nature, the concurrence of merely physical, mechanical, or organic forces come into consideration; as, for example, of the commingling of fluid elements, of rigidity or flexibility, shock, compression, elasticity, &c., to which the action of the animal forces is often incidentally, naturally, or contra-naturally co-ordinate and subordinate. All animal operations are naturally subordinate to impressions, through which the primary vital forces are maintained in activity, but only so long as animal life remains (678, 679). It depends on these forces whether an animal life can exist and continue in perfection, be the animal endowed with mind or not, and that a thousand impressions on every part of the nervous system (which act with them in a co-ordination, partly fixed by nature and naturally necessary, and partly incidental) can develop at one time whole series of natural and subordinate animal processes, from distinct centres of animal forces (673, 687-689); at another one such process only, but all subservient to the preservation of the animal and the attainment of the ends. designed by nature (674, 681-686). In animals endowed with mind, the animal-sentient forces are subordinate to the primary vital forces, the former being, in fact, impressions of a peculiar kind (356) which act through the brain, (the centre of the animal-sentient forces,) by means of the production or operation of conceptions and material ideas, and which can thereby

develop the same series of subordinate or single processes, produced by the other impressions necessary to the preservation of the animal and the attainment of nature's objects; and with the same partly necessary and natural and partly incidental co-ordination (696). All this takes place, in order that these processes may be caused also at the same time by sensation, perception, volition, effort, desire, aversion, reflection, and choice and satisfaction of the animal, and thus it be rendered more perfect, and capable of a more independent carrying out of its proper objects (370, 371).

699. The doctrine, as to the general subordination of all animal forces to the primary vital force of the brain, may excite doubts which require a solution. In this entire work, we have taught that the most essential and the greater proportion of the animal processes necessary to life, may go on perfectly, even in sentient animals, not only absolutely, but also in their natural connection, without the assistance or co-operation of the brain; and that it is possible animals may and do exist, that have neither brain nor head, nor conceptive force, and yet can perfectly perform all the functions necessary to their animal life, by means of the vis nervosa only. How can this agree with the doctrine, that the brain is the centre of all the animal forces of animals? and that the secretion of vital spirits in it, and their circulation through the whole system of animal machines, is a primary vital force of all (675)? The animal machine which secretes the vital spirits, is not in all animals the same as that which is capable of animal-sentient forces, although the term brain has been applied to both kinds (673). All animal functions require the primary vital force of the brain, because it is necessary to the secretion and transmission through the nerves of the vital spirits; but all do not require the animal-sentient forces, inasmuch as they can be replaced by the vis nervosa only. In those animals not endowed with animal-sentient forces, the secretion and diffusion of the vital spirits is necessary to their animal processes; and, consequently, a brain endowed with a primary vital force is also necessary, since all the processes are subordinate to it (680, 690). But this brain may be diffused throughout the body, and every part may have its own brain; and their animal processes may be in subordination to the primary vital force of this

diffused brain (677, iv). If, however, the nerve-medulla in the head secretes and transmits the vital spirits only, then life ceases with the removal of the head, except in so far as vital spirits already secreted and transmitted may still remain in the nerves (661, 677, ii); until these are exhausted, various processes may go on in the body in their natural co-ordination, although no sentient actions can take place in sentient animals. The functions of the brain may be compared with a fountain supplied from a brook, which waters flowers and plants: the latter are the nerves; the fountain represents the animal-sentient force, and the brook the primary vital force. The fountain may be removed, and still the flowers may flourish, provided the sources of the brook be not cut off, but the flowers and plants live only so long as the supply of water already in the garden holds out.

CHAPTER VI.

ON OLD AGE AND DEATH.

700. After an animal has attained its growth, and all its natural transformations being completed, it has remained for a period in its state of full development, everything in its nature tends to decline. Its fluid elements are used up, and become more inspissated and earthy; its solid constituents are partly destroyed, partly rendered harder and denser; its canals are filled up and ossified. All this occurs from natural causes existing throughout the organism, and for the most part in virtue of physical and mechanical forces. The consideration of these belongs to the physiology of mechanical nature; we have only to discuss the decay of the proper animal forces.

701. In old age, the brain and nerves appear to dry up, and become flaccid; the nerves even of the organs of sense become hebete from constant use and the growth of impediments to their functions, so that external impressions are less felt, and external sensations are less readily excited. Hence the diminished activity of the sexual instincts and desires, the diminished muscular energy, the insensibility and dullness of age. Internal impressions following the same rule as external, the mental powers become enfeebled, the memory fails, the judgment is impaired and becomes slow and undecided. Hence the appearance of greater wisdom and prudence than the old really possess, &c.

702. Since every kind of animal force decays, whether manifested in the insentient, the merely sensational, or the reasoning animal, destruction naturally impends over all animals, and every animal is naturally mortal. The natural necessity of this interruption of animal life is not only shown by the laws of the economy, but also by the operation of remote physical and mechanical causes, which partly destroy-insensibly and gradually-the structure of the animal machines, partly interrupt the natural action of their forces, as well in themselves as in the mechanical machines, in a way not known. The subject belongs, however, to the physiology of the mechanism of animal bodies (Haller's 'Physiology,' § 31).

703. The termination of animal life is death, which therefore occurs when no animal force whatever exercises the slightest action on the organism (638).

704. The spiritual death of a reasoning animal is the end of its intellectual life, and takes place when not a single higher animal-sentient force exercises the slightest action in the organism. In this kind of death, sensational life and the union of body and soul may still continue (641).

705. Sensational death comprises also spiritual death, and takes place when not a single sensational force exercises the slightest action in the organism. It has been termed peculiarly the death of the animal, or the deprivation of life, since it completely destroys the connection of body and soul (640); mere animal life may, however, continue.

706. Complete death takes place when not one of all the animal forces any longer acts in the slightest degree, or when the vis nervosa has ceased to act. The popular mistake as to this kind of death has been already noticed (643).

707. Natural death occurs from the natural death of the animal forces, after the animal has attained its full growth and perfection, and takes place necessarily. Few animals, and least of all mankind, die a natural death, and death occurring under other circumstances is termed accidental, the causes of which may be found in Haller's 'Physiology,' § 959.

708. Animal death in the strict sense, or the separation of the soul from the body, whether accidental or natural, takes place, either when the natural functions of the primary vital forces altogether cease, others being subordinate to them, or when the animal-sentient forces are abolished. In the former case, it results in consequence of the entire death of the animal, which includes the separation of the soul and body; in the latter case, mere animal life may continue after such separation (640). We will consider the modes in which it may occur.

709, 710. The union of body and mind is sundered when the animal ceases wholly to exist. An animal wholly ceases to exist when its vis nervosa is abolished, together with all its natural effects in the economy. No portion of the animal machines is susceptible of vis nervosa without a suitable structure, and without vital spirits (661, 663); and cannot be supplied with the latter independently of the primary vital force of the brain or nerves, by which the vital spirits