^6 COMPARATIVE ANATOMY. 



A richer hairy covering (Ian u go) is often met with in the embryonic 

 condition as, for instance, in the human foetus than occurs later ; and this 

 fact, together with the occasional appearance of abnormally hairy individuals, 

 indicates that at one time man was distinguished by a far more abundant 

 clothing of hair than at the present day. In the normal condition the Ainos 

 and the Australians are the most hairy races. 



When pigment is present, it is always situated in cells of the 

 Malpighian layer; particular parts, as, for instance, the external 

 genitals (labia majora and scrotum), the arms, the teats, and the skin 

 of the axillse in Man, are especially well provided with it. 



The outer layer of the derma, as may be seen by a glance at 

 Fig. 15, may be divided into an outer papillary and an inner 

 reticular portion. The former contains both nerves and blood- and 



FIG. 15. SECTION THROUGH THE HUMAN SKIN. 



Sc, stratum corneum ; SM, stratum Malpighii ; Co, derma ; F, F, subcutaneous 

 fat ; NP, nerve-papillae ; GP, vascular papillae ; Natad G, nerves and vessels of 

 the derma ; SD, SD, sweat-glands, with their ducts (SD 1 , SD 1 ) ; H, hair with 

 sebaceous glands (D). 



lymph-capillaries; the latter, on the other hand, becomes lost 

 without any sharp boundary line in the sub-dermal connective- 

 tissue, and in the more or less strongly-developed fatty layer 

 (panniculus adiposus). Smooth muscle elements are distributed 

 throughout the derma ; they are particularly abundant in the 

 scrotum (dartos) and in the teats. 



The integumentary glands are tube-shaped or else berry- 

 shaped or globular. The former kind, which we must consider as 

 the most simple and primitive, include the sweat-glands and their 

 modifications (e.g. ceruminousglands); while the latter, which are 

 more highly developed histologically, are spoken of as sebaceous 

 glands. To the latter group belong the already-mentioned glands 



