THE THICK CUTIS VERA. 423 



as slight indentations in the section ; at others as long canals. 

 They are well shown in the skin of an infant (Figure 180), and 

 in a foetus of nine months. In the pig, the lower border of the 

 cutis appears to the naked eye, when seen in section, like the 

 teeth of a saw. Under the microscope, the apex of each inden- 

 tation contains the bulb of a hair. In thick hides these inden- 

 tations become clefts or canals, and we find frequently a 

 sweat-gland situated at about the middle of each. The canals 

 are oblique, as are also the hair-follicles, and the axes of the 

 two are more nearly parallel than those in the human subject. 



In thin skins the canals are either so short as hardly to pass 

 for such, or, if the hair is not of sufficient length to extend to 

 the bottom of the cutis, absent. A thick skin and the ex- 

 istence of downy hairs are, then, the conditions necessary for 

 the presence of this structure in its most marked forms. I have 

 not found them in the face, although in some individuals they 

 probably exist there, nor in the thinner skin already alluded to. 

 In the lip of the rat the long hairs are imbedded in a transpa- 

 rent, mucous-like connective tissue, and their roots are sur- 

 rounded by numerous bands of muscle. It is interesting to 

 note the fact, that under each root are to be found vertical rows 

 of fat-cells, arranged end on end like the beads of a rosary, but 

 there appears to be no cleft in the surrounding tissue to en- 

 close them. In order to obtain a preparation of skin which 

 shows these structures in their entire length, the section must 

 be made vertical to the surface, and in a direction which corre- 

 sponds with the inclination of the cleft of the hair above the 

 surface. This coincides with the fine folds or "grain" of the 

 skin. Sections made in any other direction give but a frag- 

 ment of the canal, which appears then nearly as an isolated 

 lobule of adipose tissue. Even with these precautions it is 

 difficult to obtain a good specimen, unless the razor is guided 

 by the eye and, as in embryonic skin, the canals are not large 

 enough to be seen, it is greatly a question of luck whether a 

 good section can be obtained. 



TJie blood-vessels are well shown by an injection of Berlin 

 blue in the foetus near full term. In each canal, as -well as in 

 the intervals between them, the arterioles which nourish the 

 cutis ascend from the subcutaneous system of vessels, which 

 forms a fine net-work in the panniculus adiposus. Those m 

 the canals, on reaching the lateral clefts, bifurcate, giving a 



