in] of the New Physics. 67 



question ; and they used all other knowledge as a means to 

 this end. He, on the other hand, regarded the phenomena 

 presented by living beings as a field yielding him abundant 

 opportunities for applying the new methods of physical research. 

 And we cannot wonder that from this point of view the 

 movements of animals early attracted his attention. As we 

 have just said, his great work, De motu animalium, was not 

 published until after his death, the first volume appearing in 

 1680, the second in 1681 ; but as we have also said, what is 

 printed in them had been taught publicly long before, while he 

 was as yet professor in Pisa; and indeed much of the work 

 must have been already in manuscript in those early years, for 

 his pupil Bellini, writing in 1662, refers to it as already a book. 



He himself makes quite clear his own opinion of the real 

 nature of his book. In the introduction he speaks of physiology, 

 a word which employed rarely in earlier times, by Aselli for 

 instance, was now coming into general use as a 'part of 

 physics,' and this he proposes ' to ornament and enrich by 

 mathematical demonstrations.' 



Animal movements naturally divide themselves into ex- 

 ternal movements, such as those effected by the skeletal 

 muscles, and internal movements, such as the movements of 

 the heart and of other viscera, and in general the movements 

 of the fluid parts of the body. Borelli treats of each. We will 

 consider the external movements first. 



The various movements effected by the muscles present 

 two classes of problems : the special problems, mechanical in 

 nature, of the movements effected by particular muscles; and 

 the more general problem, in a certain sense also a physical 

 one, how the substance of a muscle gives rise to movement, by 

 what changes in a muscle movement is brought about. 



A large part of Borelli's work is devoted to the special 

 mechanical problems. Vesalius, and later on Fabricius, had 

 treated of these problems in some detail, but they had treated 

 of them in a more or less loose way only. They lacked, Vesalius 

 wholly, and Fabricius to a less but still to a great extent, the 

 exact mathematical and mechanical knowledge which springing 

 up in the latter part of the sixteenth century made such rapid 



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