The controversy on the circulation had been carried on up to this time abroad rather than at home; Harvey seems to have won over to his side all the men of his own country who, by their education and acquirements, might have been fitted to array themselves against him: his lectures at the College of Physicians had apparently satisfied all his contemporaries. But now one of Harvey’s own countrymen made his appearance as the vindicator of the circulation from the misrepresentations and misapprehensions of its adversaries. This was Dr. afterwards Sir George Ent, a good scholar, a respectable anatomist, conversant with physical science generally, a gentleman by his position and profession, acquainted with all the leading men of letters and science of his time, and in particular, enjoying the friendship of William Harvey. Ent’s work is entitled ‘An Apology for the Circulation of the Blood, with a Reply to Æmylius Parisanus.’[39] In his letter to Harvey, which stands in front of the work, Ent lets it appear that he was anxious to come before the world as the advocate of the circulation; he first thought of making Primerose the particular object of his animadversions, but as this opponent had already been very effectually handled by Henry Leroy, he preferred taking Parisanus to task, the rather as in dealing with him he could also controvert Primerose where it was necessary.--Ent’s Apology is, undoubtedly, a learned, though perhaps a somewhat pompous and pedantic book; still the writer occasionally shows both wit and fancy in handling his antagonist, and always learning enough in dealing with his subject. “Nothing, indeed,” to quote Dr. Lawrence,[40] “can be more unlike than Parisanus and Ent; and it is not wonderful, therefore, that one utterly ignorant of physical science confronted by one thoroughly conversant therein--that one, without power of utterance, opposed by one gifted with eloquence--that one, sluggish and inert, in the hands of one active and full of energy, should be effectually vanquished and overcome.” We may imagine, nay, we may be certain, that Harvey was not unacquainted with Ent’s purpose to appear as the advocate of his discovery, nor with the Apology before it saw the light. Having observed the appearance of certain academical dissertations in defence of the circulation, we perceive the apostles of all new truths, namely, the youthful, at work. Were there not successive generations of men, the world would stand still; the death of the individual was not merely a necessary condition to the enjoyment of life by successive generations, but essential also to the onward progress of mankind. No man who had attained to the age of 40 years, it is said, was found to adopt the doctrine of the circulation; it had to win its way under the safeguard of the Drakes and Leroys especially, that is to say, of the youthful and unprejudiced spirits of the age.