28 LECTURE III. 



other small animals, which in theii' turn are devoured by larger 

 animals, as fishes ; and thus a pabulum, fit for the nourishment of the 

 highest organised beings, is brought back by a short route, from the 

 extremity of the realms of organic matter. 



There is no elementary and self-subsistent organic matter, as Buff'on 

 taught : the inorganic elements into which the particles of organic 

 matter pass by their final decomposition are organically recom])osed, 

 and fitted for the sustenance of animals, through the operations of 

 the vegetable kingdom. No animal can subsist on inorganic matter. 

 The vegetable kingdom thus stands, as it were, between animal 

 matter and its ultimate destruction ; but in this great oflfice plants 

 must derive most important assistance from the I* o\y gastric I/ifusoria. 

 These invisible animalcules may be compared, in the great organic 

 world, to the minute capillaries in the microcosm of the animal body, 

 receiving organic matter in its state of minutest subdivision, and when 

 in full career to escape from the organic system, and turning it back 

 by a new I'oute towards the highest point of that system. 



LECTUEE III. 



EOTIFERA. 



The animal kingdom may be likened to a cone, the species of which 

 it is constituted diminishing in number as they ascend in the scale of 

 complexity. Rising from different parts of the basal circumference, 

 the different groups reciprocally approximate, interweaving their 

 mutual affinities within a progressively closer reticulation, until they 

 finally culminate in the apex, which is crowned by Man. 



The interest with which you listened to the anatomical details of 

 those minute creatures, which, by their low grade of structure, their 

 extensive distribution and incalculable myriads, form the base of the 

 animal jiyramid, encourages me again to invite you to condescend 

 from the high sphere of your habitual studies and duties to this most 

 remote and lowly region of animal life. 



Low thoxigh the Infusoria be, and remote from man in the scale of 

 organisation — literally at an invisible distance from us — yet, by the aid 

 of the optician's science and skill, analogies may be discerned in them 

 to the human structure, which ought to enlist your sympathies with 

 the discoveries that have been made in their Microscopical Anatomy. 



