~+~— 
INTEGUMENT OF NECTURUS MACULOSUS O17 
usually scattered irregularly through the whole of the middle 
layer (fig. 12). On the sides of the body and on the margins of 
the venter the pigment is limited to a layer immediately below 
the outer compact stratum (fig..6). Both melanophores and 
xanthophores are present, but in fixed and stained material only 
the melanophores can be seen. However, in fresh material 
examined in glycerin or normal salt solution the xanthophores 
are clearly distinguished. They appear as large, horizontally 
flattened, branching cells closely packed with bright golden- 
yellow globules. The xanthophores are seldom situated deep 
in the skin, but usually lie at the level of the outermost layer of 
melanophores. 
C. Blood supply 
The skin has an abundant supply of blood, especially in the 
tail. Large blood-vessels are present in the subcutaneous tissue, 
and they probably form a horizontal plexus at that level. From 
there perpendicular branches pass outward through the compact 
layer into the middle region. In this position some break up to 
form fine capillary networks about the bodies of the glands, 
while others continue toward the surface and form a second 
capillary plexus just beneath the outer compact zone of the 
dermis. No blood-vessels, however, extend into this stratum. 
D. Elastic tissue 
Tonkoff (00; Rana) was the first investigator to employ 
modern staining methods in the study of the distribution of 
elastic tissue in the amphibian integument. Schuberg (’03) gave 
a minute description of the arrangement of fibers in axolotl, 
and his results were confirmed in general by Esterly (’04) for 
Plethodon. In later works Schuberg (’07 ¢, ’08) described the 
relation of elastic and connective tissue for many other Urodela 
and several Anura. 
For a study of the distribution of these elements in Necturus, 
tissue was sectioned horizontally as well as perpendicularly and 
stained in Weigert’s resorcin-fuchsin with van Gieson’s mixture 
