r.H. xvii. IMPORTANT MICROSCOPIC DIS CO VER1ES. \ 39 



T? Se ; tion 



a, kpiderrms. 



(Huxley) * 



attention to the tongue, and published in 1665 a careful de- 

 scription of all its nerves, vessels, and" coverings. He also 

 pointed out that the outside layer of the skin or epidermis 

 of the negro is as white as yours or mine, and that the 

 colouring matter which gives him his dark colour is con- 

 tained in a deeper layer just at the point where the epidermis 

 joins the dermis or real fibrous skin beneath (see Fig 21.) 

 This soft layer is still called 

 the ' Malpighian layer,' and 

 the different colours of the 

 skins of animals are caused 

 by little cells of colouring 

 matter which lie buried in it. 



After Malpighi had ex- 

 amined many other minute 

 structures of the human body, 

 he began next to study insects, 

 and in 1669 he published a 

 beautiful description of the silkworm. With his microscope 

 he discovered the small holes or pores which are to be seen 

 along both sides of the body of insects, and he found that 

 these pores were openings into minute air-tubes, which pass 

 into every part of the insect's body, and form a breathing 

 apparatus. He also described the peculiar vessels in which 

 the silkworm secretes the juice from which its silk is made, 

 and he traced the changes which the different parts of the 

 worm undergo as it turns into the moth. In fact, he was 

 the first man who attempted to trace out the anatomy of 

 such small creatures as insects ; a study to which men now 

 often devote their whole lives. 



But grand as Malpighi's discoveries were, a Dutchman 

 named Leeuwenhceck (born 1632, died 1723) made the micro- 



its deeper layer, or 

 Malpighian layer, c, Upper part of 

 the dermis, or true skin, d d, Per- 

 spiration ducts. 



