530 THE MICROSCOPE. 



tween these we find a fluid which is thought by Henle to 

 form the nucleoli. It has been observed, that a globule of 

 oil placed in contact with a small quantity of albumen drew 

 from it a thin coating, which enveloped the globule of oil; 

 and this albumen became coagulated, forming a cell. 

 When this globule was so surrounded, the coating became 

 wrinkled; but when placed in contact with water it 

 became distended, thus proving it to be capable of endos- 

 mosis, or more probably an absorption of water by the 

 wall of the cell, which in consequence became distended or 

 swollen up, as there is no attraction between oil and water. 

 Nevertheless, elementary granules appear to be granules of 

 oil, surrounded by a covering of a protein compound. 

 Milk globules, being composed of oil, surrounded by a 

 covering of casein and dissolved fibrin, have been shown to 

 attract a covering of albumen. 



In this way the chyle, for instance, is taken as food into 

 the body. The chyle is composed of protein compounds 

 and fatty matters, which are reduced to a pulp by the 

 digestive process; the protein compounds being converted 

 into albuminous matters. The villi throughout the intes- 

 tinal canal are permeable to these fluids ; the oily particles 

 meeting with a protein compound, are attracted to them, 

 forming a covering, and so an elementary granule is 

 produced. In their subsequent development, cells, if 

 fully formed, never lose their character as cells while they 

 exist; but they may dissolve other cells before they are 

 changed into certain tissues. Cells may receive additional 

 parts, which may remain as such, or form tissues; such 

 are termed complicated cells : nerves and muscular fibre 

 are formed from these. Examples of cells that undergo 

 no further metamorphosis after full development are 

 found in the cells of the epithelium, epidermis, and in 

 the corpuscles of the blood. The elementary con- 

 stituents of glands are cells, and the fluids are absorbed 

 by them: they are the great agents of absorption and 

 secretion. 



Change of Cells into Tissues. This may take place by a 

 joining together or coalescence of cells in a rudimentary 

 state. Cells may meet, and at the point of contact coalesce 

 and run into each other, thus forming a tube; indeed, 



