124 PROGRESS OF SCIENCE. 



dermis or true skin, and the perspiration ducts (1665). He 

 was really the earliest investigator of the lungs, the skin, and 

 the mucous membrane. He also investigated the formation 

 of the chicken in the egg. He was the first anatomist, too, 

 who studied the ANATOMY OF INSECTS and revealed their 

 marvellous structure : his description of the silk-worm (1669) 

 in particular made a deep impression, giving as it did an idea 

 of the breathing, circulation, secretion, growth, and metamor- 

 phosis of the insect ; so that Malpighi started THREE im- 

 portant biological BRANCHES the physiology of plants, insects, 

 and animals. 



1632 1723. Leuwenhoeck, by means of microscopes 

 made by himself, studied the Infusoria, and discovered 

 the Rotifers and other animalcules of the infusorial group 

 living either in water or in the body of other animals 

 showing that a speck, no larger than a grain of sand, 

 may be made up of eight or ten thousand living crea- 

 tures. He was a worthy rival of Malpighi. His " Epistolae 

 Physiologicae " were much in advance of his time. The study 

 of Infusoria, of which he was the chief pioneer, has been 

 immensely enlarged by Ehrenberg (1795 1868?), who has 

 demonstrated that these minute creatures have internal 

 structures similar to those of higher animals. He has 

 described over five hundred species, some of which he dis- 

 covered in fog, rain, and snow. 



1637 80. Swammerdam improved the art of dissecting, 

 applying it to the general history of INSECTS ; determined 

 the degree of blood-heat in animals by means of a new ther- 

 mometer; described the rise of lymphatic vessels, lately 

 discovered by Riidbeck ; compared the history of bloodless 

 animals with that of plants ; composed the history of blood- 

 less animalcula a work unsurpassed in anatomical accuracy. 



1668 1738. Boerhaave made the medical school of 

 Leyden famous by his successful labours, which attracted to 

 Holland numerous students, several of whom became cele- 

 brated physicians. Besides the beneficial impulse he gave to 

 Medicine, he founded ORGANIC CHEMISTRY the pursuit, 

 that is, of chemical analysis of the substances composing plants 

 and animals. Anatomists had described the structure and 



