THE PROBLEM QF CIRCULATION
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It appears, then, that Galen’s sources of evidence respect-
ing the motion of the heart were the same as Harvey’s —
viz. comparison of structure in a variety of animals, argu-
ment from the use of these structures, observation of the
living heart, and numerous experiments on animals.
It may be asked, Why, if Galen had a correct method and knew most of the facts so accurately, did he not discover the circulation ? The difference of structure be- tween human anatomy and that of the inferior animals, which was Galen’s weak point, did not come in here. But why did not Vesalius, or Fabricius, or Colombo, whose anatomical knowledge was quite as complete as was re- quired, get near it ? The fact seems to be that the problem was one of those in which you must be wholly right or wholly wrong. It is like those word-puzzles in which a number of letters are thrown on the table to make a word. No combination except the right one is much nearer the truth than another. The word is not spelt till the right combination is effected. So in this problem the mere accumulation of correct data was of little avail. Galen made a marvellously ingenious combination of letters, but it did not spell the right word. Harvey had no difficulty in showing that Galen was inconsistent with himself— more inconsistent, indeed, than those who knew less. Servetus and Colombo, who knew the lesser circula- tion, and Fabricius, who described the valves of the veins, equally failed, and were still more inconsistent h At last
1 It is remarkable that in the edi- tion of Fabricius’s tract on the valves of the veins, published at Frankfort, 1624, we find a figure of the veins of the arm as tied up for bleeding, showing the situation of the valves, which was afterwards adapted by Harvey to make the well-known dia- grams in his book De Motu Cordis, showing the use of the valves. Har- vey’s engraver must have been directed to copy Fabricius’s plate (which is thus necessarily reversed)
C
on a reduced scale. Harvey's Figure t, accordingly, is a reduced copy of Fabricius’s plate, while in Figures 2, 3, and 4 the hands are added to show the experiments described in the text. As both works were printed at Frankfort within a few years, very likely the plates were executed by the same engraver, especially as the character of the lines and cross- hatching is identical.
It is very singular that Fabricius, having so carefully studied the valves o
