18 INTRODUCTION. LiECT. I. 



my efforts will be rewarded by the great benefit you will 

 derive therefrom. It is perhaps the first time that a course 

 of lectures, under this name, has been introduced into 

 medico-physical education. We have no work which 

 treats exclusively of this subject : the germs, indeed, are 

 scattered here and there, but hitherto they have never 

 been viewed in the light most favourable for their develop- 

 ment. 



If at the commencement of a course of lectures the 

 teacher usually finds it requisite to give an exact defini- 

 tion of the science he is about to treat of, to show its 

 limits and its objects, in a word, to sketch a plan and 

 programme of his course, assuredly the necessity for such 

 preliminaries was never more obvious than in the present 

 instance. 



General Properties of Living Beings. Living beings are 

 endowed with the general properties of all natural bodies. 

 The most ultra- vitalist never dreamt of denyingthat living or- 

 ganized matter is extended, impenetrable, divisible, and po- 

 rous. How can we believe that caloric, electricity, light, and 

 chemical affinity, act on these beings in a manner entirely 

 different from that which they are known to do on the other 

 bodies of nature ? 



Yet you will find in some much-esteemed works on 

 Physiology, tables of the differences between, and even of 

 the presumed opposite characters of, organic and inorganic 

 bodies. I should enter into a long and useless discussion, 

 were I to attempt to demonstrate to you that many of these 

 pretended differences have little or no value. Animals 

 and vegetables grow by intussusception, minerals by juxta- 

 position ; in other words, in the former, growth takes 

 place by internal juxtaposition, in the latter by external 

 juxtaposition ; for organized bodies conceal in their interior 

 the dissolved elements of new formations, whilst, on the 



