92 THE MICROSCOPE. 



the Pterodactyle bone, and differed essentially from 

 that of every known bird that no one who placed 

 much reliance upon that evidence could entertain the 

 slightest doubt on the matter. By Professor Owen, 

 however, the validity of that evidence was questioned, 

 and the bone was still maintained to be that ot a bird ; 

 until the question was finally set at rest, and the value 

 of the microscopic test triumphantly confirmed, by 

 the discovery of undoubted Pterodactyle bones of cor- 

 responding, and even of greater dimensions, in the 

 same and other chalk quarries."* 



CHAPTER IX. 



THE MICROSCOPE IN PHYSIOLOGY. 



BY the aid of the microscope we become acquainted 

 with the wonderful structure of skin and other animal 

 tissues. This figure represents a section of human skin, 

 which is found to consist of two principal layers the 

 cutis vera, or true skin, and the cuticle, or epidermis, 

 which covers it. A thin vertical section of the skin 

 of the finger shows the upper layer, or cuticle, at a; the 

 lower part, or cutis vera, at b; sweat-glands, e, with 

 their ducts, at c, leading to the orifices ; the small 

 granular clusters at / are fat-cells ; the dull-coloured, 

 wavy portion at b is the rete mucosum, or stratum 

 Malpighii. Mingled with the cells which make up 

 the epidermic covering are found others, which, from 

 their secreting colouring matter, are called pigment- 

 cells. An extraordinary number of blood-vessels, 

 twisting so as to form a complete network of capillaries 

 and numerous nerves, are distributed through the cutis 



* Dr. Carpenter, page 764. 



