16 THE MICROSCOPIST. 



minute anatomy of the kidneys, spleen, liver, membranes of 

 the brain, &c., and several of the structures still retain his name. 

 He also paid attention to the anatomy and transformations of 

 insects, the development of the chick in the egg, and the struc- 

 ture of plants. It will be perceived from the last remark, that 

 the intimate connexion between animal and vegetable physiology 

 was even then acknowledged. This connexion has led to the 

 establishment of the cell doctrine, or the theory of the develop- 

 ment of all organized tissues from cells. 



Lewenhoeck has sometimes been called the father of micro- 

 graphy. He was born at Delft, in Holland, in 1663, and 

 appears to have received a rather indifferent early education. 

 He first brought himself into notice by the skill with which he 

 ground glasses for microscopes and spectacles, and for improve- 

 ments in those instruments ; thus affording a good model for 

 microscopic observers : first attending to the optical and 

 mechanical construction of the instrument he was to employ. 

 In 1690 he discovered and demonstrated the capillary blood- 

 vessels. He opposed the chemical doctrines which then reigned 

 in medicine, which attributed disease to fermentation in the 

 blood. He objected ; that if fermentation existed, air bubbles 

 would be seen in the vessels, which was not the case. He 

 showed that the blood-globules were of different sizes and forms 

 in various tribes of animals ; examined the brain and nerves, 

 the muscles, the crystalline lens, the milk, and numerous other 

 textures and fluids ; and made the interesting discovery of the 

 spermatozoa, which he conceived to be of different sexes. There 

 can be no doubt that he made numerous errors, but the whole 

 subject being new, his errors were excusable; and his contribu- 

 tions to science are still of the highest interest. 



Swammerdarn, Lyonet, and Ellis, after this period, greatly 

 extended our knowledge of the lower tribes of animals; while 



