350 REPORT OF THE COMMISSIONER OF FISHERIES. 
overcome their effects. The tautog, besides the appearances cited, has 
almost invariably small elongate blebs between the rays of the pectoral 
and usually.also the caudal fin. The small sculpin (JZyoxocephalus 
wneus) seldom fails to develop in the skin of the belly an emphysema 
of a honeycomb structure; and often in the later stages, by coalescence 
or enlargement, vesicles containing several cubic centimeters of gas 
may form, floating the fish belly upward long before it finally succumbs. 
Very young puffers (Spherotdes maculatus, fig. 1, pl. 1), when only 
half an inch long, develop vesicles at the base of the caudal fin some- 
times as large as the entire body of the fish, which buoy it to the 
surface and keep it there in spite of its struggles to descend. The 
pipe-fish (Siphostoma fuscum) usually shows vesicles about the snout. 
In the seup (Stenotomus chrysops), both large and small (2-inch), the 
first indication of the presence of gas is seen in the protrusion of the 
eyeballs, bringing about the condition known as pop-eye. 
These external lesions, however, though interesting and important 
in their bearing on the explanation of the disease, are not sufficient to 
cause death. Aside from some occasional bloody streaks in the fins, 
eyes, or muscles, neither constant nor characteristic, no external lesions 
other than these are to be found and no adequate cause of death is to 
be seen. It is on laying open the dead or dying specimens that the 
fatal lesion is disclosed. A remarkable and striking picture presents. 
The blood vessels contain notable quantities of free gas, the amounts 
varying greatly, from a few small bubbles scattered through the larger 
vessels to a quantity which may distend the bulbus of the heart even 
to several times its normal bulk, stretching its walls to a thin mem- 
brane, tense and firm with the pressure of the gas contained to the 
entire exclusion of the blood, the whole resembling the air bladder of 
a small fish. The auricle may be still beating without propelling any 
blood. The fish may live for some time, probably for days, even after 
considerable quantities of gas have separated; for upon killing and 
opening scup not yet in the death struggle the gas has been plainly 
discerned. The walls of the auricle and ventricle may be emphysema- 
tous. The branchial artery or ventral aorta is often empty of blood 
and tense with the pressure of gas, while in the gills is found perhaps 
the most constant and significant lesion. The main vessel of the gill 
filament usually has its lumen filled with gas (fig. 2, pl. 1), which is 
often seen just entering the capillaries that branch from this vessel. 
But these capillaries it seldom fills. The gas plugs of the gill fila- 
ments are usually present—though not always-—even when the evi- 
dences of gas within the body are not very marked. A fatal embolism 
results, and death is due to stasis.* When nearly all the filaments are 
atn these typical cases of embolized gill filaments and of a distended heart, no assumption of any 
form of initial cardiac paralysis seems necessary. The stasis must haye occurred in spite of cardiac 
effort. 
