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, hoth 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 S3^stem and organs of sense. 

 VIII. The development of the hody. 

 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. 



§ 16. 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, Avith 

 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, fiuorido 

 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 o'cjanic chc/iiidr//. 

 Tl\esc very complex chemical groups of elements are called the 

 pvo.rimatc elemeni>i 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 arc 

 grouped in two classes : 1. I'hosc called nitrogenous, because con- 

 taining nitrogen, and 2, the non-nUro(jc)iot(s, because destitute of that 

 element. Most of the component substances of the body, such, c.<j., 

 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 alhunicn, and that of jelly, called (jehitinc, form the types. 

 Fats, on the contrary, arc 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 

 arc also spoken of as 2)t'otvid, because they have been supposed to be 

 derived from an imaginary substance termed 2)rotein, consisting of 

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

 as forms oi protojilmin.'^ About four-sevenths of the weight of the 



* A tfnn proposed hy Molil to denote I ciTatiirc is at fust oiitirely coinposcd of 

 the soft iiiti-rioi- of cells. Every living ' this (iimteruary compound. 



