THE MICROSCOPE IN ANIMAL HISTOLOGY. 185 



XI. Mineral Constituents. Oxygen, Nitrogen, Carbonic 

 acid. Water. Hydrochloric acid. Silicic acid. Calcium 

 compounds (Phosphate, Carbonate, Chloride, and Fluor- 

 ide). Magnesium compounds (Phosphate. Carbonate. 

 Chloride). Sodium compounds (Chloride. Carbonate. 

 Phosphate. Sulphate). Potassium compounds (Chloride. 

 Carbonate. Phosphate. Sulphate). Salts of Ammonium 

 (Chloride. Carbonate). Iron and its Salts (Protochloride. 

 Phosphate). Manganese. Copper. 



The subject of Histology relates properly to cell-struc- 

 ture (already described, Chapter IX), and its morpho- 

 logical products, yet its close connection with Histo-chem- 

 istry renders the foregoing list of substances valuable to 

 the student. 



II. HISTOLOGICAL STRUCTURE is due to the formative 

 power of bioplasm, or living cell-substance, and is not mere 

 selection and separation from pabulum, or aliment, since 

 from the same pabulum, and, so far as we can see, under 

 the same circumstances, result tissues having different 

 physical and chemical properties. 



In our classification we have arranged the microscopic, 

 or histological, elements of the tissues as Granules, Glob- 

 ules, Fibre, and Membrane. 



Granules are minute particles of formed material. 



Globules are small, homogeneous, round, or oval bodies. 

 If composed of albuminous matter they are rendered trans- 

 parent by acetic acid, and are dissolved by potash and 

 soda. If consisting of fat they are soluble in ether and 

 unaltered by acetic acid. If they are earthy matters they 

 are dissolved by acids and unchanged by alkalies. 



Fibres appear as fine lines, cylindrical threads, or flat- 

 tened bands, parallel, or at various angles. 



Membrane is an expansion of material. It may be trans- 

 parent and homogeneous, and may be recognized by plaits 

 or folds, which sometimes simulate fibres, or it may be 

 granular, or bear earthy particles. 



