240 THE CAT. [chai>. vni. 



eight nipples — four on each side, one close to the anterior, and one 

 near the hinder end of the glandular structure. 



These glands heconic greatly enlarged when in use, especially the 

 abdominal portion (Fig. 114). In the male the mammary gland is 

 quite rudimentary, though essentially similar in structure to that of 

 the female. 



These milk glands may he regarded as greatly enlarged and aggre- 

 gated sebaceous glands, and the milk which they secrete, as a modified 

 sebaceous secretion. The milk they form is an opaque white fluid, 

 containing much water, v/ith certain salts of potassium and sodium, 

 with phosphoric acid, iron, milk-sugar, some albuminous matters 

 (casein and a little albumen), with fats and some other substances. 



The milk beiug the destined food of the kitten, contains all the 

 materials needed for the nourishment and growth of the young 

 animal. It contains in fact a suitable and nicely balanced supply 

 of nitrogenous and non-nitrogenous, albuminoid, fatty, amylaceous 

 and saccharine matters. 



§ 19. In the structures last described v,'e have found organs 

 destined for the nourishment of another individual ; but we have 

 next to consider organs destined for the actual fonnafioii of other 

 individuals. Such are the organs of RErRODUCTioN, or generative 

 organs : the business of which is to manufacture, and to render 

 serviceable certain diverse products which concur in giving rise to 

 a new living organism, destined with groM'tli to become an animal 

 like that b}^ which one or other of such products have been secreted. 



The products thus formed are essentially of two kinds, and the 

 faculty of forming one or the other of them constitutes the difference of 

 iscj['. It is only by the union of these two kinds of products that a new 

 cat can be formed, and the pj'ocess by which that formation takes place 

 after such a union has been effected, is the process of development, the 

 consideration of whicli will occupy us in the next chapter but one. 



But although the process of development will there be considered, 

 the nature of generation may be moi-e fitly spoken of here. The 

 process of growth has been already many times referred to, and 

 even in the second chapter facts as to the growth of epithelial cells, 

 of cartilage and bone, were brought before the reader's notice ; and 

 in the chapter on the organs of circulation, we saw how lymph 

 corpuscles grow by spontaneous self-division within the substance of 

 the lymphatic glands. In all these })roccsses of growth, Ave have, 

 indeed, already become acquainted with a sort of I'eproduction, for 

 it is by Ihc re})roduction of the component cells of the various tissues 

 that their growth is effected. The fact then of an organ secreting 

 cells which detach themselves in order to perform special functions, 

 is a fact which has now no novelty for us. Indeed wo have met 

 with a truly complex form of reproduction, in the development 

 from the milk-tooth's sac of a bud or olf-shoot, capable of growing 

 into the permanent dental structure by which such milk-tooth is 

 ultimately replaced. Nevertheless, although generation may be 

 said to be a kind of growtli ; yet it is a very special and peculiar 

 kind of growth. 13y it in the first place is formed a cell capable by 



