148 EMBRYOLOGY IN THE SEVENTEENTH [pt. 11 



even by the eye, by reason of their contract invisible dimensions (like 

 those Atomes, that fly in the aire) which are scattered and dispersed 

 up and down by the winds ; all which are esteemed to be Spontaneous 

 issues, or born of Putrefaction, because their seed is not anywhere 

 seen." Unfortunately, he never returned to this subject, for, as he 

 himself informs us in another place, all the papers and notes in his 

 house in London were destroyed at the time of the Civil War, so that 

 what he had written on the generation of insects irretrievably 

 perished. 



Another point on which Fabricius had been in error was the ap- 

 pearance of bone and cartilage in the embryo. According to him, 

 "Nature first stretcheth out the Chine Bone, with the ribbes drawn 

 round it, as the Keel, and congruous principle, whereon she foundeth 

 and finisheth the whole pile". This armchair conceit Harvey was 

 easily able to destroy by a mere appeal to experience, but by ex- 

 perience also he came upon a fact less easily to be explained, namely, 

 that the motion of the foetus began when as yet there was hardly any 

 nervous system. "Nor is it less new and unheard of, that there should 

 be sense and motion in the foetus, before his brain is made; for the 

 Foetus moves, contracts, and extends himself, when there is nothing 

 yet appears for a braine, but clear water." On the basis of this 

 paradox Harvey may be said to be the discoverer of myogenic con- 

 traction, but he already could claim that distinction, for the first 

 heart-beats are accomplished long before there are any nerves to the 

 heart, as he himself points out. "We may conclude from this fact", 

 he remarks, "that the heart and not the brain is the first principle 

 of embryonic life", and he gives instances of physiological actions 

 not under the conscious control of the individual, such as the reflexes, 

 as we should call them, of the intestinal tract, and the emetic action 

 of infusion of antimony which cannot be tasted much and "yet there 

 passeth a censure upon it by the Stomack" and a vomit ensues. Thus, 

 twenty-five years before Francis Glisson, Harvey had formulated, 

 from embryological studies, the view that irritability was an intrinsic 

 property of living tissues. 



Both Harvey and Fabricius were very puzzled about the first 

 origin of the blood. "What artificer", says Harvey, "can transform 

 the two liquors into blood, when there is yet no liver in being?" 

 It was to be a long time before this question was answered by Wolflf 's 

 discovery of the blood islands in the blastoderm, and, even now, the 



