7O BIOLOGY AND ITS MAKERS 
Ruysch. In 1664 he discovered the valves of lymphatic 
vessels by the use of slender glass tubes, and, three years 
later, first used a waxy material for injecting blood-vessels. 
It should be noted, in passing, that Swammerdam was the 
first to observe and describe the blood corpuscles. As early 
as 1658 he described them in the blood of the frog, but not 
till fifty-seven years after his death were his observations 
published by Boerhaave, and, therefore, he does not get the 
credit of this discovery. Publication alone, not first observa- 
tion, establishes priority, but there is conclusive evidence 
that he observed the blood corpuscles before cither Malpighi 
or Leeuwenhoek had published his findings. 
Love of Minute Anatomy.—After graduating in medi- 
cine he did not practice, but followed his strong inclination 
to devote himself to minute anatomy. This led to differences 
with his father, who insisted on his going into practice, but 
the self-willed stubbornness and firmness of the son now 
showed themselves. It was to gratify no love of case that 
Swammerdam thus held out against his father, but to be 
able to follow an irresistible leading toward minute anatomy. 
At last his father planned to stop supplies, in order to force 
him into the desired channel, but Swammerdam made efforts, 
without success, to sell his own personal collection and pre- 
serve his independence. His father died, leaving him suffi- 
cient property to live on, and brought the controversy to a 
close soon after the son had consented to yield to his wishes. 
Boerhaave, his fellow-countryman, gathered Swammer- 
dam’s complete writings after his death and published them 
in 1737 under the title Biblia Nature. With them is in- 
cluded a life of Swammerdam, in which a graphic account is 
given of his phenomenal industry, his intense application, his 
methods and instruments. Most of the following passages 
are selected from that work. 
Intensity as a Worker.—He was a very intemperate 
