PROTOPLASM. , I 



likely that in the human body, copper, manganesium, alumi- 

 nium, and lead are merely accidental elements, which, being 

 taken in minute quantities with the food, and not excreted 

 at once with the faeces, are absorbed and deposited in some 

 tissue or organ, of which, however, they form no necessary 

 part. In the same manner, arsenic, being absorbed, may 

 be deposited in the liver and other parts. 



CHAPTER III. 



STRUCTURAL COMPOSITION OF THE HUMAN BODY. 



IN the investigation of the structural composition of the 

 human body, it will be well to consider in the first place, 

 what are the simplest anatomical elements which enter 

 into its formation, and then proceed to examine those 

 more complicated tissues which are produced by their 

 union. 



It may be premised, that in all the living parts of all 

 living things, animal and vegetable, there is invariably to 

 be discovered, entering into the formation of their anato- 

 mical elements, a greater or less amount of a substance, 

 which, in chemical composition and general characters, is 

 indistinguishable from albumen. As it exists, in a living 

 tissue or organ, it differs essentially from mere albumen 

 in the fact of its possessing the power of growth, develop- 

 ment, and the like ; but in chemical composition it is 

 identical with it. 



This albuminous substance has received various names 

 according to the structures in which it has been found, and 

 the theory of its nature and uses which may have pre- 



c 2 



