SWAMMERDAM. 133 



method of injecting arteries with coloured wax, and 

 of keeping the internal organs in a dry condition 

 for purposes of study, and investigated the nature 

 of the lymphatics. He graduated soon after, and 

 after receiving his diploma, returned to his old 

 love, nature, and occupied nearly all his time in the 

 anatomy and physiology of insects. 



Swammerdam worked so incessantly, that he got 

 into bad health, and was obliged to relinquish 

 the medical profession for a time. He followed 

 up his researches into the minute construction of 

 insects, and really never ceased them until death. 

 The Grand Duke of Tuscany visited Amsterdam 

 at this time, and examined Swammerdam's col- 

 lections. Greatly impressed with their value, and 

 with the splendid dissections, he offered a home 

 to the young naturalist in his palace, and twelve 

 thousand florins for the collection. Swammerdam, 

 however, did not care to wear a collar ; and loving 

 freedom of thought, which he did not think he 

 would have in Italy, declined the offer. He knew 

 that he would be expected to change his religious 

 tenets, and said that he would not sell his soul for 

 money. He published a " General History of 

 Insects," in 1669, and soon afterwards broke down, 

 entirely, in health, so that he had to go into the 

 country to rest and do nothing. But this was im- 

 possible; and he began to study bees, and their 

 natural history. Probably it was this constant 

 weak health, and the solitude necessary for the 

 peculiar nature of his work and observations, that 



