42 LECTURE IV. 



also, in the Formation of the Mud which is deposited in the Bed 

 of the Elbe at Cuxhaven, and upon the Agency of similar Phe- 

 nomena in the Formation of the Bed of the Nile, at Dongolar, in 

 Nubia, and in the Delta of Egypt." * " Truly, indeed," says Ehren- 

 berg, " the microscopic organisms are very inferior in individual 

 energy to lions and elephants, but in their united influences they are 

 far more important than all these animals." 



LECTURE IV. 



ENTOZOA. 



The ancient philosophers styled man the microcosm, fancifully con- 

 ceiving him to resemble in miniature the macrocosm or great world. 



Man's body is unquestionably a little world to many animals of 

 much smaller size and lower grade of organisation, which are 

 developed upon and within it, and exist altogether at the expense of 

 its fluids and solids. 



Not fewer than eighteen species of internal parasites, or of those 

 which infest the internal cavities and tissues of the human body, have 

 been enumerated ; and of these, at least fourteen are good and well 

 established species of Entozoa. 



Hippocrates and Aristotle had distinguished the human intestinal 

 worms by the names of " Helminthes stronguloi" and " Helminthes 

 plateiai ; " but the study of these parasites in general has been re- 

 served for recent times. Since the time of Linnaaus the stimulus 

 which that great master gave to every branch of Natural History has 

 been in no department more potent than in encouraging researches 

 into the before neglected field of the Internal Animal Parasites. 



To the labours of Bloch, Goeze, Zeder, and, above all, to those of 

 Rudolphi, we are indebted for our knowledge of these animals as an 

 extensive class, which Rudolphi has characterised, under the name of 

 Entozoa, as white-blooded worms without respiratory organs, and 

 (but less accurately) without nerves. 



The number of these Parasites may be conceived when it is stated 

 that almost every known animal has its peculiar species, and generally 

 more than one ; sometimes as many as, or even more kinds than, infest 

 the human body. 



* Edinb. Philos. Journal, vol. xxxi, p. 386". 



