12 THE CAT. [CHAP. i. 



of each organ and set of organs, together with their structure, and to 

 treat of them in the following order : 



I. The skeleton, both external and internal. 

 II. The parts which act upon the skeleton to effect motion the 

 muscles. 



III. The organs of alimentation. 



IV. The organs of circulation. 



V. The organs of respiration and secretion. 

 VI. The generative organs and reproduction. 

 VII. The nervous system and organs of sense. 

 VIII. The development of the body. 

 IX. Psychology. 



The facts of structure and function having been disposed of, we 

 may proceed to consider the various affinities of the cat to other 

 animals, its relations to space and time, and the question of its 

 origin. 



15. Before, however, commencing the proposed description, it 

 may be well to state briefly a few facts as to the chemical composition 

 of the body. 



The body of the cat is chemically composed of four principal 

 elements, namely, oxygen, hydrogen, nitrogen, and carbon, with 

 small quantities of other elements sulphur, phosphorus, chlorine, 

 fluorine, silicon, potassium, sodium, calcium, iron, and magnesium. 

 These elements are united together so as to form water, carbonate 

 of lime, chlorides of sodium and potassium, sulphates and carbonates 

 of soda and potash, phosphates and carbonates of magnesia, fluoride 

 of calcium, and ammonia, and they are ultimately united into very 

 complex groups of elements, termed "organic" compounds, the 

 study of which pertains to a special science called organic chemistry. 

 These very complex chemical groups of elements are called the 

 proximate elements of the body because they are the first component 

 substances into which it can be dissolved when in course of being 

 reduced to its ultimate elements. Such proximate elements are 

 grouped in two classes : 1. Those called nitrogenous, because con- 

 taining nitrogen, and 2, the non-nitrogenous, because destitute of that 

 element. Most of the component substances of the body, such, e.g., 

 as the flesh and the blood, are composed of the first, or nitrogenous, 

 proximate elements, of which the substance of the white of egg, 

 called albumen, and that of jelly, called gelatine, form the types. 

 Fats, on the contrary, are non- nitrogenous substances, and consist 

 only of oxygen, hydrogen, and carbon, or if they contain other ele- 

 ments, nitrogen is not amongst them. The nitrogenous substances 

 are also spoken of as protcid, because they have been supposed to be 

 derived from an imaginary substance termed protein, consisting of 

 oxygen, hydrogen, nitrogen, and carbon. They are also spoken of 

 as forms of protoplasm.* About four-sevenths of the weight of the 



* A term proposed by Mold to denote 1 creature is at first entirely composed of 

 the soft interior of cells. Every living ' this quaternary compound. 



