32 MICROSCOPIC ILLUSTRATIONS. 



menagerie of living wild beasts on the large scale ; and 

 most certainly many of them wonderfully emulate the 

 ferocity, voracity, cunning, and cruelty of the mammalia. 

 They prey on each other, and fight with a degree of 

 determined obstinacy, not inferior to that of any beings 

 whatever. They have likewise a thousand diverting 

 pranks and humours, quite peculiar to themselves. In 

 addition to these amiable and amusing qualities, they 

 possess such a high degree of transparency, that their 

 unique and beautiful internal machinery is as clearly 

 perceptible as if they were made of glass ; so that, with- 

 out any dissection, we can unravel all the mysterious 

 workings of their nature ; such as the circulation of the 

 blood, the pulsations of the heart, the peristaltic motion 

 of the intestines, and the play of every muscular fibre. 

 This property of transparency is not possessed by any 

 other living beings with which I am acquainted, except 

 the Animalcula infusoria. I may observe, that no perfect 

 insects present so many facilities for adaptation to the 

 microscope, or can be so easily preserved and managed; 

 so that the larvae, &c. appear to me peculiarly and ex- 

 clusively devoted to the consideration of microscopists*." 

 Having now given a brief outline of the uses to which 

 the microscope may be applied, we will proceed to con- 

 sider those practical improvements which, in modern 

 times, the instrument itself has undergone, and which, 

 step by step, have at length brought it to its present 

 high state of perfection. 



* Exordium, first edition, p. 6. 



