62 BIOLOGY AND ITS MAKERS 
conditions he was not destined to live many years. He died 
there, in 1694, of apoplexy. His wife, of whom it appears. 
that he was very fond, had died a short time previously. 
Among his posthumous works is a sort of personal psycholog 
written down to the year 1691, in which he shows the growth 
of his mind, and the way in which he came to take up the 
different subjects of investigation. 
In reference to his discoveries and the position he occupies. 
in the history of natural science, it should be observed that 
he was an “ original as well as a very profound observer.” 
While the ideas of anatomy were still vague, ‘‘ he applied him- 
self with ardor and sagacity to the study of the fine structure 
of the different parts of the body,” and he extended his inves- 
itgations to the structure of plants and of different animals, 
and also to their development. Entering, as he did, a new 
and unexplored territory, naturally he made many discover- 
ies, but no man of mean talents could have done his work. 
Activity in Research.—During forty years of his life he 
was always busy with research. Many of his discoveries had 
practical bearing on the advance of anatomy and physiology 
as related to medicine. In 1661 he demonstrated the struc- 
ture of the lings. Previously these organs had been regarded 
as a sort of homogeneous parenchyma. He showed the pres- 
ence of air-cells, and had a tolerably correct idea of how the 
air and the blood are brought together in the lungs, the two 
never actually in contact, but always separated by a mem- 
brane. These discoveries were first made on the frog, and 
applied by analogy to the interpretation of the lungs of the 
human body. He was a comparative anatomist, and the 
first to insist on analogies of structure between organs 
throughout the animal kingdom, and to make extensive 
practical use of the idea that discoveries on simpler animals 
can be utilized in interpreting the similar structures in the 
higher ones. 
