40 



LECTURE m. 



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 pyramid, 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 though 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 sympa- 

 thies with the discoveries that have been made in their Microscopical 

 Anatomy. 



Time was, and not many years ago, in this country, when that 

 term. Microscopical Anatomy, was almost regarded as synonymous 

 with the anatomy of the imagination : but the numerous and highly 

 important discoveries which have been made and confirmed by 

 observers in almost every European state, by means of the greatly 

 improved microscopes at their command, have placed the value, the 

 indispensability, of that instrument to the anatomist, beyond the 

 necessity of vindication. 



Some scepticism may be natural and pardonable, when the anatomy 

 of an animalcule xoVo" ^^ ^ ^^^^^ ^^ diameter is attempted to be 

 demonstrated : but trace it to its source, and you will find such 

 incredulity to be essentially based, not merely on distrust in our 

 means of observation, but in the difficulty of adequately conceiving 

 the relations of size. Just ideas of these relations are essential to the 

 acceptance and full appreciation of the discoveries which have extended 

 for us the bounds of space ; and I will ask permission to quote the 

 words of one of our old philosophers, which bear directly on this 

 subject, and, expressing a noble confidence in intellectual progress, 

 shed a prophetic gleam upon the present improved powers of pene- 

 trating space. 



" In consistency, I suppose some bodies to be harder, others softer, 

 through all the several degrees of tenacity. In magnitude, some to 

 be greater, others less, and many unspeakably little. For we must 

 remember that, by the understanding, quantity is divisible into 

 divisibles perpetually. And, therefore, if a man could do as much 

 with his hands as he can with his understanding, he w^ould be able to 

 take from any given magnitude a part which should be less than any 

 other magnitude given. But the omnipotent Creator of the world can 

 actually from a part of any thing take another part, as far as we by 

 our understanding can conceive the same to be divisible. Wherefore 

 there is no impossible smallness of bodies. And what hinders but 



