HUMAN HISTOLOGY 



GENERAL REMARKS. 



THE human body, when fully developed, is composed of solids 

 and fluids, in the proportion of one of the former by weight to at 

 least eight or ten of the latter. 1 All the solids are permeated to a 

 greater or less extent by the fluids, of which, also, water is always 

 the principal constituent. The mere descriptive anatomist regards 

 the solids alone, as if isolated from the fluids which form an essen- 

 tial part of them. But the chemical physiologist and the histologist 

 must study the latter as well as the former. The isolated fluids, 

 also, as the blood, chyle, milk, and other secretions, corne within 

 the domain of histology so far as they contain cells, granules, nu- 

 clei, or other histological elements ; and these, therefore, as well as 

 the tissues, will be embraced in this work. 



Commencing, however, with an analysis of the human body as 

 seen by the unaided eye, and omitting for the present the isolated 

 fluids, we find that it is composed 



1. Of parts and organs. 



2. That the organs are formed of combinations of tissues. 



3. The tissues are composed of certain chemical compounds called 

 immediate principles. 



4. And the last are formed by a direct combination of a few of 

 the simple chemical elements. 



Reversing this view, we perceive that 



1. The simple elements unite to form the immediate principles. 



2. The last unite to form the tissues. 



1 A mummy of a native of Teneriffe, presented to Blumenbach by Sir Joseph 

 Banks, weighed but seven pounds and a half; probably not more than one-sixteenth 

 of the weight of the same body during life. 



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