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[p. 153]of a vacuum to become refilled? For, although according to Erasistratus, it contains within itself a cavity of sorts, this is not occupied with blood, but with psychic pneuma,
According to the Pneumatist school, certain of whose ideas were accepted by Erasistratus, the air, breath, pneuma, or spirit was brought by inspiration into the left side of the heart, where it was converted into natural, vital, and psychic pneuma; the latter then went to the brain, whence it was distributed through the nervous system; practicallly this teaching involved the idea of a psyche, or conscious vital principle. Psychic pneuma" is in Latin spiritus animalis (anima-pysche); cf. p. 126, note 4. Introduction, p. xxxiv.
and we are required to imagine the nutriment introduced, not into this cavity, but into the vessel containing it, whether it needs merely to be nourished, or to grow as well. How, then, are we to imagine it introduced? For this simple vessel [i.e. nerve] is so
small- as are also the other two- that if you prick it at any part with the finest needle you will tear the whole three of them at once. Thus there could never be in it a perceptible space entirely empty. And an emptied space which merely existed in theory could not compel the adjacent fluid to come and fill it.
At this point, again, I should like Erasistratus himself to answer regarding this small elementary nerve, whether it is actually one and definitely continuous, or whether it consists of many small bodies, such as those assumed by Epicurus, Leucippus, and Democritus.
Observe that Erasistratu's "simple nerve" may be almost looked on as an anticipation of the cell. The question Galen now asks is whether this vessel is a "unit mass of living matter," or merely an agglomeration of atoms> subject to mechanical law. cf Galen's "fibres," p. 329.
For I see that the Erasistrateans are at variance on this subject. Some of them consider it one and continuous, for otherwise, as they say, he would not have called it simple; and
some venture to resolve it into yet other elementary bodies. But if it be one and continuous, then what is evacuated from it in the so-called insensible transpiration of the