APPLICATION OF THE MICROSCOPE 21 



at once attracted me; finally, since this also has its own 

 difficulties I applied my mind to the study of plants, intend- 

 ing after prolonged occupation with this domain, to retrace 

 my steps by way of the vegetable kingdom, and get 

 back to my former studies. But perhaps not even this will 

 be sufficient ; since the simpler world of minerals and the 

 elements should have been taken first. In this case, however, 

 the undertaking becomes enormous and far beyond my 

 powers." 1 There is something fine in this life of broad 

 outlines, devoted whole-heartedly to an idea, to a plan of 

 research, which required a lifetime to carry out. 



An important histological discovery dating from this 

 time is that of the finer structure of muscle, made by Stensen 

 (or Steno) in 1664. He described the structure of muscle- 

 fibres, resolving them into their constituent fibrils. 



To the microscope we owe not only histology but the com- 

 parative anatomy of the lower animals. Throughout the I7th 

 and 1 8th centuries the discovery of structure in the lower 

 animals went on continuously, as may be read in any history of 

 Zoology. 2 We content ourselves here with mentioning only 

 some representative names. 



In the i /th century Leeuenhoek, applying the microscope 

 almost at random, discovered fact after fact, his most famous 

 discovery being that of the " spermatic animalcules." 



Swammerdam studied the metamorphoses of insects and 

 made wonderfully minute dissections of all sorts of animals, 

 snails and insects particularly. He described also the 

 development of the frog. It is curious to see what a grip 

 his conception of metamorphosis had upon him when he 



1 " Etenim, fervent! aetatis calore, Anatomica aggressus, licet circa 

 peculiaria fuerim solicitus, in perfectioribus tamen haec rimari sum 

 ausus. Verum, cum haec propriis tenebris obscura jaceant, simplicium 

 analogismo egent ; inde insectorum indago illico arrisit ; quae cum et 

 ipsa suas habeat difficultates ad Plantarum perquisitionem animum 

 postremo adjeci, ut diu hoc lustrato mundo gressu retroacto Vegetantis 

 Naturae gradu, ad prima studia iter mi hi aperirem. Sed nee forte hoc 

 ipsum sufficiet cum simplicior Mineralium Elementorumque mundus 

 praeire debeat. At in immensum excrescit opus, et meis viribus omnino 

 impar," Opera Omm'a, i., p. i, London, 1686. 



2 See particularly E. Radl, loc. cit., \ Teil. J. V. Cams, Geschichte 

 der Zoologie, Miinchen, 1872. 



