A HISTORY OF SCIENCE 



comparison with modern physicians. There is, how- 

 ever, another side to the picture. His knowledge of 

 anatomy was certainly very considerable, but many of 

 his deductions and theories as to the functions of or- 

 gans, the cause of diseases, and his methods of treating 

 them, would be recognized as absurd by a modern 

 school-boy of average intelligence. His greatness must 

 be judged in comparison with ancient, not with mod- 

 ern, scientists. He maintained, for example, that 

 respiration and the pulse-beat were for one and the 

 same purpose that of the reception of air into the 

 arteries of the body. To him the act of breathing 

 was for the purpose of admitting air into the lungs, 

 whence it found its way into the heart, and from there 

 was distributed throughout the body by means of the 

 arteries. The skin also played an important part in 

 supplying the body with air, the pores absorbing the 

 air and distributing it through the arteries. But, as we 

 know that he was aware of the fact that the arteries 

 also contained blood, he must have believed that these 

 vessels contained a mixture of the two. 



Modern anatomists know that the heart is divided 

 into two approximately equal parts by an impermeable 

 septum of tough fibres. Yet, Galen, who dissected 

 the hearts of a vast number of the lower animals ac- 

 cording to his own account, maintained that this sep- 

 tum was permeable, and that the air, entering one side 

 of the heart from the lungs, passed through it into 

 the opposite side and was then transferred to the 

 arteries. 



He was equally at fault, although perhaps more 

 excusably so, in his explanation of the action of the 



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