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In Pisa he laboured twelve years, and in 1668 returned to his old 

 University of Messina, where he remained until 1674. Sicily at that 

 time belonged to Spain. Borelli was suspected of some political con- 

 spiracy. In any case, he fled to Rome, where he came under the 

 patronage of Queen Maria Christina, daughter of Gustavus Adolphus 

 of Sweden. Adolphus died in 1644, but Christina, after a short 

 term of queenship, preferred to reside in Rome. During all these 

 years, Borelli had been labouring at his great work, De Motu 

 Animalium. Christina promised to defray the expense of its publica- 

 tion, but did not. Misfortune overtook him, and in 1677, after this 

 misfortune, he lived with and taught in the Society of the Scholre Pise 

 of San Pantaleone until his death, in 1679. His great work was not 

 published until after his death : the first volume in 1680, the second 

 in 1681. It is somewhat remarkable how it escaped the strict censor- 

 ship of the Church at that time. 



The problems of motion in man and animals, resistance of air and 

 water, the limbs as levers, the mechanism of voluntary and mixed 

 movement, the movements of the heart and chest engaged his attention. 

 He regarded respiration as due to contraction of the diaphragm and 

 the intercostal muscles and the elasticity of the air. The air yielded 

 to the blood in the lungs a sal mice. Some of the problems remained 

 much as he left them, until E. H. Weber attacked them again in the 

 middle of last century. He anticipated the experiments of Reaumur 

 and others on the contractile force of the gizzard in birds. 



Borelli studied not only the movements as brought about by 

 muscles, or groups of muscles, but also the problem of how 

 muscles change their form. In connection with the latter problem, 

 we must remember that the microscope was now being used by 

 anatomists. Malpighi was using it in Pisa. In 1664 Nicolas 

 Stensen Steno published a little tract, De Musculls Observationum 

 Specimen, which took the title of Elementorum Myologice Specimen 

 in 1667. The work is illustrated by bold diagrams of the arrange- 

 ment of fibres in various muscles. Stensen had a very fair knowledge 

 of the general build of a muscle. He even noticed the difference in 

 colour between what we now know as the red and pale skeletal 

 muscles of the rabbit. 



Borelli, like Stensen, recognised that the fleshy part, and not the 

 tendinous part, was the real contractile part. In the original figure 

 it is marked " caro." 



The mechanical problems of the circulation, of course, arrested 

 Borelli's attention. He figures the general arrangement of the 

 muscular fibres of the heart, and endorses the view of Harvey, that 

 the blood is propelled by the systole of the ventricles, as in the action 

 of a winepress. Naturally, as a mathematician, he attempted to 

 estimate the force, or mechanical value, of the systole of the ventricles. 



