[45] BIOLOGY OF THE RHINE SALMON. AT1 
sinks till the consumption of matter and the loss of matter are equalized, 
still leaving something for self-consumption. 
Sometimes, however, circulation sinks very low, like fish which in spring 
have been entirely sucked out by leeches. Some salmon show shortly 
before and during the spawning period small and large ulcers, with lim- 
ber undermined bands and adhesive yellow scabs, at the bottom of which 
muscles and bones are laid bare. Such ulcers are not only, as in former 
times, found back of the lower jaw (where they may have been caused 
by constant rubbing against rocks or stones), but more particularly at 
the basis of the rays of the fins, at the tail, and sometimes on the oper- 
culum. Sometimes an entire ray becomes gangrened and falls off. In 
other parts of the body, especially on the jaws, there may be seen raised, 
yellow, opaque spots, void of blood, which are probably the forerunners 
of the ulcers. Fish in this condition are positively sick, and the epi- 
thelium, gradually tearing to shreds, indicating a disturbance of its pro- 
cess of nutrition, may well be compared to the tongue of a patient who 
is very low witha fever. The flesh of the trunk is entirely opaque, whit- 
ish, and full of little grains of fat. Even the heart, which has long re- 
mained intact, shows in many cases numberless fibers filled with little 
grains of fat, and to the naked eye shows a brownish color, whilst the 
inner layers of its flesh are quite tender. 
What a different appearance is presented by fish which have passed 
the spawning period ten days, or, better still, some weeks (empty female 
fish, caught at the end of December or in January; but also one speci- 
men from Mr. Glaser’s fish-boxes, which certainly had lost its eggs not 
longer than ten days ago). The skin is again bluish, clear, and shining; 
the ulcers have become cicatrized or are healing; the flesh is transpar- 
ent, entirely or nearly free from grains of fat; even the fibers of the 
heart are beginning to be purified, and in the intestines there is no trace 
of food. The ovarium contains more or less eggs, which, imbedded in 
a serous and occasionally somewhat suppurated secretion of the follicle 
skin, shrivel in the most manifest manner, and become absorbed. It is, 
therefore, a sort of nutrition, as it were—a little pocket-money for the 
return voyage. The greatest importance, however, I am inclined to 
ascribe to the pale, shriveled-up follicle skins. The collateral blood- 
channels of the ovarium have become closed (by contraction of the ves- 
sels). The salmon resembles a patient who, after Hsmarch’s bandage 
has been placed on his leg, has had that limb amputated. Its blood 
circulates within narrower limits, therefore with a higher pressure, and 
supplies a smaller quantity of substance than ever before with oxygen; 
the circulation again satisfies all @emands upon it, and the muscle of 
the trunk again becomes normal. But the difference of color of the 
extracts with water, between the greatly reduced muscle of the trunk 
and the muscles of the fins which have remained intact, has become 
alarmingly small. Vital organs are now attacked, and what little nu- 
tritive matter is furnished by the ovarium is partly consumed by the 
