the use of respiration that either an absolutely minute quantity, or none at all, of the substance of the air, is taken into the heart."[35]

It is clear, however, that Galen, when delivering himself of the foregoing, was a trifle carried away by the ardor of contention; for in the very treatise to which he refers us, as well as elsewhere, he not only dilates upon the cooling effects of breathing, but admits the entrance of air into the heart for a definite physiological purpose. This purpose, however, which we shall study later, is not cooling and is counted of secondary importance by Galen. Nevertheless, he goes so far as to say this:—

"That some portion of the air is drawn into the heart in its diastole and fills the vacuum which is produced, is sufficiently shown by the very magnitude of the dilation."[36]

In his treatise "On the Use of the Parts of the Human Body" Galen takes a more judicial tone in the following brief, calm summary:—

"The use of the respiration of animals arises from the heart, as has been shown. The heart itself needs in some sort the substance of the air; but, first and foremost, it craves to be cooled, because it boils with heat. The heart is cooled by the cool quality of inspiration; but expiration also cools, by pouring out that which seethes within the heart and is, in a way, burned up and sooty."[37]

Thus do we see the modern products of respiration foreshadowed.

Galen believed that the heat of animals is safeguarded also by the entrance of cooling air through the pores of the skin into the arterial system, and by the exit through these pores of injurious fumes out of the arteries.[38] In the introduction to Harvey's great treatise of 1628[39] the English physician riddles with adverse arguments this doctrine of Galen; to this we shall return later, as we shall to Galen's belief that the brain draws cooling air directly into its ventricles out of the nares through the cribriform plate of the ethmoid bone.[40]

In passing from Aristotle to Galen we have crossed nearly five centuries. Now let us pass at a leap across fourteen centuries more, from Galen at imperial Rome under Septimius Severus to Harvey at London under King James the First. Having briefly scanned the doctrines of the Greeks, let us take up our study of respiration in Harvey's private lecture notes of 1616. His crabbed handwriting has been deciphered by experts, and his notes have been both photographed and printed. If we seek therein for his thoughts about respiration, and track them through the jungle of abbreviated careless Latin and racy English in which they were jotted down, we shall find them Galenic in part, but also denying a truth which Galen had accepted. Harvey's notes are often too disconnected for quotation, calling rather for paraphrase or summary; and to make either is a task which one cannot approach without diffidence, especially as this task involves translation also. Of what I have ventured to prepare to represent parts of Harvey's note-book in the present paper some passages are simple translations, such English words as Harvey interspersed being transcribed. Naturally such passages are included between quotation marks. These are not used, however, in the case of a paraphrase or summary, even if it contains scattered English words which are Harvey's own.

Harvey fully shared the ancient view of the supreme importance of the heat of animals. In his note-book he, like Galen, deals with respiration under the heads: first, of a possible absorption of some of the substance of the air; and, second, of cooling and ventilation. Let us first take up the second head. Harvey says:—

"Without nourishment life cannot be, nor nourishment without concoction, nor concoction without heat, nor heat without ventilation;" for heat perishes either of wasting or of smothering; "so there is cooling and ventilation of the native heat, ventilation especially."[41]

His words contain reminders of Aristotle;[24] and he continues about respiration in a vein as ancient as Hippocrates,[42] as follows:—

"Nothing is so necessary, neither sense nor food. Life and respiration are convertible terms, for there is no life without breathing and no breathing without life. If the eye be cut out there is an end of seeing; if the legs be cut off there is an end of walking; if the tongue, of speech, et cetera; if respiration, there is an end of everything immediately."[43]

When Harvey jotted this down he had in mind a Galenic passage which doubtless had become the common property of all physicians in his day; for the removal of eye and legs figures in the first chapter of Galen "On the Use of Respiration."[44] Harvey continues:—

"Hence large animals are much warmer and breathe frequently, because they have need of greater cooling and ventilation inasmuch as they very greatly abound in blood and heat."[45]

In the margin opposite this passage there is written:—

"Why and how air is needed by animals which breathe and also air is necessary to a candle and to fire see W. H."

We may conjecture that this note refers to Harvey's promised treatise on respiration, which was never published.

So far Harvey has simply reiterated the ancient doctrine of cooling and ventilation, as in the passages