34 



CHAPTER I. 



SOLID AND FLUID CONSTITUENTS OF ANIMAL BODIES. PROXIMATE 



PRINCIPLES. SECONDARY ORGANIC COMPOUNDS. CLASSIFICATION 



OF THE TISSUES. DEVELOPMENT OF THE TISSUES FROM CELLS. 



PROPERTIES OF THE TISSUES. 



ANIMAL bodies are composed of solids and fluids. The former 

 constitute the various textures and viscera ; the latter, the blood, 

 lymph, chyle, and the liquid secretions of glands contained, either 

 in their excretory ducts, or in special reservoirs. 



The solid textures contain only about one fourth of solid matter, 

 the rest is water. The great shrinking which they experience, when 

 dried, shews how much of their bulk they owe to this combination ; 

 and parts thus shrunken swell out again, and assume their natural 

 condition on the addition of water. The mummy of a large man 

 is of a very trifling weight. Blumenbach possessed the entire per- 

 fectly dry mummy of a Guanche or aboriginal inhabitant of Tene- 

 riffe, presented to him by Sir Joseph Banks, which, with all its 

 muscles and viscera, weighed only seven pounds and a half. 



Water is one of the most important constituents of animal 

 bodies. It forms four fifths of their nutrient fluid, the blood ; and 

 it gives more or less of flexibility and softness to the various solid 

 textures. The loss of it in great quantity speedily puts a stop to 

 vital action, as may be easily shewn in the lower animals; and some 

 animalcules, in which all appearance of life may have ceased on 

 being deprived of it, will revive on its being supplied to them again. 

 It is a solvent of many organic matters ; some also are suspended 

 in it : it is, therefore, a valuable medium for conveying these sub- 

 stances to the several textures and organs. It plays a most im- 

 portant part in the various chemical operations of the body ; and 

 its addition to, or subtraction from a particular compound is capable 

 of converting it into a substance of very different properties. 



By anatomico-physiological analysis we separate the solids and 

 fluids of the body into their various kinds, and classify and arrange 

 them according to their characters and properties. 



