Chapter 2
The Relationship Between
The Two Basic Animal Forces
And The Alternating Movement
Of The Nervous System
370. In order to determine better the nature and characteristics of the two basic animal forces, we must first examine their manner of activity in a particular case.
We have supposed that the whole nervous system alternates its insensitive movements in the direction of both extremities or poles of the nerve, so that the movement is either to the external extremity or pole, or contrariwise to the internal extremity or pole (cf. 355). These two unceasing movements in fact correspond to the two basic animal energies we have indicated (cf. 369). The extension of the nerves towards the external extremity is clearly a movement that presupposes a fundamental feeling in act, and can only be the effect of the sensuous instinct. This instinct, aroused by stimuli, uses spontaneous movement to obtain new sensations to which it is inclined. Hence the withdrawal of the nerves to a state of rest is produced solely by the life instinct because this instinct governs both the production and conservation of feeling, and therefore relaxes the nerves, returning them to their original and, as it were, natural state.(173)
Notes
(173) According to Boerhaave, sleep is so natural to human beings that they would go on sleeping if no stimulus disturbed their body. This great man's opinion would seem to agree with what we have said, namely, that stimuli arouse the nerves, whose movement therefore begins with respiration at the moment the foetus makes contact with air and light. Brown's opinion would also seem true. According to him, life is a kind of forced or excited state, produced by certain stimuli. Whatever the truth of these opinions, we must say that the exercise of external life cannot be incessantly continued, because it requires a certain effort whose continuation brings about changes in the organs and corporeal structures. Prof. Medici suggests that these changes, to which he thinks the structures are subject, are mechanical and chemical. He thinks the alteration of the mechanical state of the structures `consists in a change of disposition, forms or adhesion in the integral particles of the structures themselves as a result of long, repeated movements of the organic filaments'. The alteration of the chemical state of the structures `if indeed it takes place, arises from a greater loss of matter, the effect of the same vital movements of the structures. Because of this loss the organic compound would not be sufficiently preserved' (cf. Manuale di Fisiologia, Bologna, 1835).