LIMITING FACTORS IN THE HISTORY OF SCIENCE 



goes deeper than words, however, for it involves the concepts of the 

 investigator. What the Germans call "Begriffsbildung" or the con- 

 struction of concepts congruent with certain sorts of natural pheno- 

 mena, though never conscious in the history of biology, has none 

 the less been operative. In this field we may remember the doctrine 

 of Galen concerning the natural faculties (Sum/xet?), and the im- 

 mense length of time which was required for biologists to see that it 

 was nothing more than a concise statement of the phenomena them- 

 selves. Not until it was "seen through" as an explanation was post- 

 Renaissance biology possible. Similarly, the peculiar contribution of 

 Leonardo to embryology was his realisation that embryos could be 

 measured at a succession of moments. The application of the concept 

 of change in weight and size with time, a concept which, as modem 

 biology shows, admits of much accuracy when properly worked 

 out, was thus first made by Leonardo. In the same way Boyle^ was 

 the first to see clearly that a problem of mixture is presented by the 

 developing embryo (though Hippocrates had stated it dimly some 

 two thousand years before). If the embryo is made up of mixed 

 things, some definite proportion and way of mixture must exist. 

 And no hope of finding out what this was could be obtained from 

 the Aristotelian elements (heat, cold, moisture, and dryness) or from 

 the Alchemical principles (salt, sulphur, and mercury). Hence Boyle*s 

 emphasis on the corpuscularian or mechanical hypothesis, and all its 

 historical implications. 



His preference for the "mechanical or corpuscularian" philosophy 

 was mainly due to his realisation that unless chemistry was going to 

 start measuring something it might as well languish in the obscurity 

 to which Harvey would willingly have relegated it. Thus he says: — 



"But I should perchance forgive the Hypothesis I have been 

 examining (that of the alchemists), if, though it reaches but to 

 a very little part of the world, it did at least give us a satisfactory 

 account of those things which 'tis said to teach. But I find not 

 that it gives us any other than a very imperfect information even 

 about mixt bodies themselves; for how will the knowledge of 

 the Tria Prima?' discover to us the reason why the Loadstone 

 drawes a Needle, and disposes it to respect the Poles, and yet 

 seldom precisely points at them } How will this hypothesis teach 



^ The Sceptical Chymist, l66l. 



^ The three alchemical (hypostatical) principles. 



149 



