CH. xxiv. COMPARATIVE ANATOMY. 197 



will feel the part under your hand swell up and grow hard. 

 The reason of this is that the muscle of your arm, called the 

 biceps, has contracted, or grown shorter and thicker, in the 

 process of bending your arm. If you open your arm again, 

 the swelling will go down, because the muscle is stretched out. 

 Now before Haller's time it was thought that the muscles 

 could not contract of themselves, but were drawn up by the 

 nerves. Haller discovered that this is not so, but that a 

 muscle, if irritated, will draw itself together, even when it is 

 quite separated from the nerves, and this has since been 

 proved to be true by a great number of experiments. So 

 that though it is true that our nerves are the cause of our 

 moving, because they excite the muscles and so make them 

 contract, yet the real power of contraction is in the muscle 

 itself. 



Comparative Anatomy, or the Comparison of Dif-\ 

 ferent Structures in Men and Animals. John Hunter. 1 

 Another point in which Haller did good service to science I 

 was in comparing the same parts of the body of men and ' 

 animals, and showing how far they are alike. This study, 

 which is called the study of comparative anatomy, has now - 

 become very important, for by examining any organ, such as 

 the heart, for example, from the lower animals in which it is 

 very simple, up to man in whom it is complicated, we can 

 tra^e its gradual improvement, and understand it much more 

 perfectly. Aristotle and Vesalius had both of them com- 

 pared some of the parts of different animals, and so had 

 other and later zoologists ; but Haller was the first to make 

 ; t a regular study, and John Hunter, who lived about 

 same time, devoted his whole life to it, and raised 

 rank of a separate science. 



John Hunter, who was born in the County of Lanark, \ 

 in 1728, was the brother of a very eminent London phy; 



.bout thej 

 it to thel 



