346 THE MICROSCOPE. 



our acquaintance with the true composition of every organ in the body, 

 have been arrived at by means of the microscope, and could never 

 have been known without it. 



In addition to this, and what is of greater importance, after having 

 studied the healthy structure of the body, most beneficial aid is afforded 

 in the diagnosis of diseases, which in many cases were overlooked 

 or undistinguishable without the assistance of this instrument. It is 

 on this account constantly resorted to by the medical profession for the 

 benefit of their fellow-creatures. 



The space allotted to this division of our subject enables us to 

 give only a short and imperfect sketch of a few of the fundamental 

 tissues of the animal body. First, enumerating merely the elementary 

 substances recognised by chemistry as entering into the formative 

 processes, we shall proceed to inquire into that most interesting and 

 wonderful starting-point of life, the cell; now admitted to be, and indeed 

 demonstrable as, the common centre alike of the animal and vegetable 

 organism. 



THE HUMAN BODY, ITS PHYSIOLOGICAL COMPOSITION AND 

 CHARACTER. 



The elementary 'substances found in the human body are oxygen, 

 hydrogen, carbon, azote, phosphorus, sulphur, chlorine, fluorine, iron, 

 manganese, titanium, and lime. Silinium is found in the hair, and 

 flourine in combination with lime forms the enamel of the teeth. Iron 

 is the colouring-matter of the blood, the black pigment of the choroid 

 of the eye, and in the skin. 



Manganese is found in the bones, hair, blood ; titanium in the 

 salts from the supra-renal capsule. Other substances and gases are 

 found distributed throughout the body. 



Azotised and now-azotised substances constitute the proximate or- 

 ganic principles. The azotised are, protein and its compounds, albu- 

 men, fibrin, casein, and pepsin ; extractive matters, gelatin, hsematin, 

 colestrin or bile matters, urea, and uric acid. The now- azotised are, 

 lactine, or sugar of milk, and fatty matters. 



Cells. All animal and vegetable structures, it has been found by 

 microscopists, are developed from cells ; the materials for these in ani- 

 mals are furnished from the yelk and the blood. 



A nucleated cell, 1 a, Plate XII., is a delicate membrane of a glo- 

 bular form, enclosing a granulous fluid j in the wall on one side is a 

 dark oval body this is the nucleus : there are one or two, seldom 



