552 A. B. DAWSON 
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muscles are seen in surface view. Figure 21 represents such a 
section. Near its center the entire muscle wall has been cut 
away, exposing an epithelial nucleus and some secretion. At 
the top the fibers have been sectioned somewhat obliquely to 
their long axes. Near the bottom the surface of the muscle 
fibers is barely exposed, and zigzag’ striae are seen extending 
across them. The markings remind one somewhat of the appear- 
ance presented by the outer edges of the myomeres of a fish 
when the muscle has been exposed by the removal of the skin. 
In more nearly median sections of the gland, where the fibers 
are seen in longitudinal section, the striations appear as ragged, 
tooth-like projections along the outer edges of the muscles. 
Further, around every contracted gland there are strained regions 
in the connective tissue caused by the enormous decrease in the 
volume of the gland. The striations therefore are probably due 
to some connection between the muscle fibers and the surround- 
ing connective tissue, the resistance offered by the connective- 
tissue fibers as the muscles contract resulting in some way in 
the production of ridges on the-outer surfaces of the latter. The 
zigzag or wavy course of these transverse markings is possibly 
caused by variations in the amount of contraction in individual 
fibers. 
b. Of the mucous gland. As already noted, mucus appears 
on the surface of the animal very readily. Any slight mechanical 
stimulus will induce a discharge. The effects of handling and 
of killing in chloroform have already been mentioned. Ammon- 
ium hydroxide or other irritating reagents applied to a limited 
area, when the animal is out of water, cause a strong flow of 
secretion from the mucous glands: in that region only. When 
the animal is returned to the water, secretion is still discharged, 
giving rise to cord-like masses of mucus which float up in the 
water. The quantity of mucus obtained by any vigorous chemi- 
cal or mechanical stimulation is enormous, being many times 
greater in volume than the skin by which it is produced. The 
secretion apparently swells when it comes in contact with the 
water, and moisture seems to be necessary in order that mucus 
be discharged freely. If an animal be taken from the water and 
