GALEN. 



UNDER the Ptolemies a powerful stimulus was given to 

 biological studies at Alexandria. Scientific knowledge 

 was carried a step or two beyond the limit reached by 

 Aristotle. Thus Erasistratus and Herophilus thoroughly 

 investigated the structure and functions of the valves of 

 the heart, and were the first to recognize the nerves as 

 organs of sensation. But, unfortunately, no complete 

 record of the interesting work carried on by these men 

 has come down to our times. The first writer after 

 Aristotle whose works arrest attention is Caius Plinius 

 Secundus, whose so-called " Natural History," in thirty- 

 seven volumes, remains to the present day as a monument 

 of industrious compilation. But, as a biologist properly 

 so called, Pliny is absolutely without rank, for he lacked 

 that practical acquaintance with the subject which alone 

 could enable him to speak with authority. Of informa- 

 tion he had an almost inexhaustible store; of actual 

 knowledge, the result of observation and experience, so 

 far as biological studies were concerned, he had but 



