XXIX.] THE SKIN. $25 



advantage, that it is not changed by exposure to light, hut the 

 tissue must be hardened before sections are cut. 



13. V.S. Injected Skin, e.y., Palm. The section should be cut 

 in paraffin, and include the subcutaneous tissue (fig. 311). 



(a.) (L) The arteries of the skin are branches of the larger 

 arteries in the subcutaneous tissue. A branch may be seen running 

 towards the surface. In its course it gives off three independent 

 sets of branches, which end in capillaries : 



(i.) The lowest to the groups of fat-cells, where it forms a net- 

 work of capillaries around and between the fat-cells. 



(ii.) The short branch to the coil of a sweat-gland, forming a rich 

 network of capillaries between the coils of the tube. 



(iii.) The highest is from the terminal branches of the artery, 

 and splits up into capillaries, which form a network chiefly in the 

 upper part of the corium, and from this branches pass which form 

 capillary loops in the papilla? of the skin. From it also proceed 

 branches to the hair-follicle and its sebaceous gland. 



(l>.) The vein arises from the capillaries of the papillae and the 

 branches of the arteries to the upper part of the cutis, and in its 

 course running near the corresponding artery it collects the 

 veinlets from the coil and masses of fat. For blood-vessels of skin 

 see W. Spatleholz. 1 



14. Under-Surface of Epidermis. Separate by one of the follow- 

 ing methods the epidermis from the cutis, most easily done in the 

 foetus: (a.) Use a foetus that has died and been macerated in utero. 



(b.) Place pieces of skin in J-J per cent, acetic acid (1-3 days^, 

 adding a drop or two of chloroform to prevent putrefaction 

 (Phttippson). 



(r.) Macerate at 40 C. preferably foetal or young skin pinned 

 out on cork in 6 per cent, (or weaker) wood vinegar for 1-2 days. 

 The epidermis separates rapidly (Loewy). 2 



After the epidermis peels off, in all cases turn its deeper surface 

 upwards, and stain it for 3-4 minutes with a watery solution of 

 Pxx'hmer's logwood (p. 68). Wash and mount in balsam, pre- 

 ferably without a cover-glass. 



(L) Observe a system of septa crossing each other, and forming 

 longitudinal and transverse ridges, which project into the cutis. 

 They form, as it were, the negative picture ; the papillae of tho 

 cutis vera represent the positive image. Part of the cells lining 

 the sweat-glands and hair-follicles may also be pulled out, and are 

 turned toward the observer. Figures of the arrangement of these 

 septa are given in the papers of Blaschko and Loewy (pp. 316, 325)- 



1 Archiv f. Anat. v. Phys., Anat. Abth., 1893. 



2 Arckwf, ntik. Anat., xxxvii. p. 159, 1891. 



