448 Natural- Historical Collections. 



of the principal viscera, and must furnish new occasions for observing. But 

 this journey became infinitely more profitable when the Ptolemies were masters 

 of the country. These enlightened princes, emulous of contributing to the pro- 

 gress of human knowledge, gave permission to dissect to several Greek physi- 

 cians. Their protection placed anatomists beyond the reach of popular fury ; but 

 it could not preserve them from the atrocious calumnies which were disseminated 

 against them. It was even pretended that they had dissected living men. 



The first who obtained a name among the anatomists, the chief of the 

 school, if we may thus express ourselves, is an Asclepiad of Cos, named Praxa- 

 goras, contemporary of Theophrastus, and probably a disciple of Aristotle. It was 

 he who first gave a name to the arteries, and established the distinction between 

 these vessels and the veins, demonstrating that the latter contained blood after 

 death, whilst the others are entirely empty. He first showed that the pulse exists 

 in the arteries. Medical men, it is true, in the time of Hippocrates, and even 

 anterior to that period, made use of the indications of the pulse ; but they did not 

 take into account the origin of this motion. Praxagoras, who made this disco- 

 very, had no notion of the circulation of the blood. 



Two other medical men, still better known, are Herophilus and Erasistratus, 

 who both lived principally in Egypt. Herophilus, bom in Chalcedonia, was of 

 the family of Asclepiadac. He was a pupil of Praxagoras, and became afterwards 

 the physician of Ptolemy, son of Lagns. It is to him that belongs the merit of 

 having discovered in the nerves the organs of sensation and volition, and of hav- 

 ing carefully distinguished them from tendons, ligaments, and other white tissues 

 with which they were previously confounded. He described different parts of the 

 brain ; the curvature of the corpora striata ; the choroid plexus ; the calamus scrip- 

 torius ; and, lastly, that vascular arrangement which, in the present day, we call, 

 from his name, torcnlar Herophili. He described the internal membranes of 

 the eye ; the hyoid bone ; the pulmonary vein, which he calls arterial vein. He 

 also gives to a part of the small intestines the name of duodenum. Lastly, he re- 

 cognized the isochronism of the pulsations of the heart and arteries. It would 

 appear that there was only one step further to the discovery of the circulation ; 

 a;nd yet Herophilus had no more idea of it than Paraxagoras. 



Eristratus, born in the island of Cos, attended, during some time, the lectures 

 of Aristotle, of whom he was the grandson ; and, after the death of this philosopher, 

 he attached himself to Theophrastus. He was physician to Seleucus Nicanor; 

 and every body knows how he discovered the love which the son of this prince, 

 Antiochus Soter, had for his mother-in-law, Stratonice. He afterwards quitted 

 Syria and came to Alexandria, where he devoted himself with ardour to the study 

 of human anatomy. His labours are considerable. We are indebted to him for 

 the capital discovery that all the nerves terminate in the brain either immediately 

 or through the medium of the spinal marrow. He compared the brain of man to 

 that of a great number of animals, and not only in a general manner, as Aristotle' 

 had done, but taking it part by part. He recognized the lacteal vessels on a kid 

 that had just suckled. He was acquainted with the internal valves of the heart, 

 and described the tricuspid valves. This was another step towards the know- 

 ledge of the circulation, which he, nevertheless, did not arrive at ; and an inter- 

 val of more than seventeen centuries elapsed between his discovery and that of 

 Servetus. He even thought that the air passed from the lungs into the arteries, 

 and from thence into the heart ; and it was on this idea that he based his prac- 

 tice. Erasistratus founded at Pergamus a school of medicine, which perpetuated 

 itself to the fourth century. He was, like Herophilus, very learned in botany. 

 The works of these two medical men are lost ; and we only know of their labours 

 by the mention which Galen has made of them. 



While the learned men of the museums were causing science to advance at 

 Alexandria, some travellers continued to go to distant countries in search of in- 

 formation. Thus, Megasthenes, who had been sent by Nicanor to a king of 

 India, whom the Greeks have called Sandrocottus, wrote a relation of his jour-' 



