344 ANIMAL NATURE AS A WHOLE. [in. 



forces, that is to say a centre wherein all the natural connect- 

 ing points of the animal forces are collected together, since in 

 all, there are found, at very distinct portions of the nervous 

 system, larger and smaller ganglia, plexuses, and general points 

 of division of nervous trunks into branches. If, however, those 

 centres of the animal forces ought to be termed general, which 

 are common to all animals without exception, then there are 

 many such (673) ; or if by the expression is meant a certain 

 portion of the animal machines [the nervous system], the 

 injury, destruction, or removal of which terminates life, then 

 there certainly are such general centres, as we shall shortly 

 show (675) ; but those are in general in greatest number which 

 are mutually subordinate to each other. 



675. The heart and brain are essential to animal life in all 

 animals, the latter as the secreting organ of the vital spirits, 

 the former as the first cause of the circulation. Both are the 

 most important and the first visible portions of the germ. It 

 is true, that the brain in the embryo of sentient animals has 

 no apparent function, for its natural visible movement seems 

 to be requisite to the action of its animal-sentient force, be- 

 cause it only occurs with respiration, and consequently not 

 before birth (24) ; anteriorly to which no animal-sentient force 

 can be shown to be in operation (634). On the other hand, 

 the secretion of the vital spirits is an invisible function (28), 

 and in so far as it is animal is a pure vis nervosa (374, 159), 

 which may without doubt be active in utero. The heart, or its 

 analogue, manifests a distinct movement in the earliest stage of 

 development of the embryo : these two centres must conse- 

 quently be considered to be the primary and essential portions 

 of the system of animal machines. We therefore term the 

 secreting faculty of the brain and the natural force of the 

 heart, the primary vital forces. We exclude from this desig- 

 nation the animal-sentient force of the brain, which is not com- 

 mon to all animals, and understand solely the two mentioned, 

 the one being that on which all animal forces depend, without 

 exception; and the other that on which the circulation, the 

 secretions, and nutrition are dependent 



676. It may happen, that before birth an animal receives its 

 fluids from its mother, elaborating none by its own forces, and 

 secreting none until it has an independent existence. The vital 



