350 EEPOET OF THE COMMISSION EK OF FISHERIES. 



overcome their effects. The tautog, besides the appearances cited, has 

 ahijost invariablj" small elongate blebs between the ra3"s of the pectoral 

 and usually also the caudal fin. The small sculpin {Mijoxocejplialus 

 ceneus) seldom fails to develop in the skin of the ])elly an emphj^sema 

 of a honeycomb structure; and often in the later stages, hy coalescence 

 or enlargement, vesicles containing several cubic centimeters of sfas 

 YH^y form, floating the fish bell}' upward long before it finally succumbs. 



Ver}^ 3^oung puffers {SpJieroides maculatus, fig. 1, pi. ii), when onl}^ 

 half an inch long, develop vesicles at the base of the caudal fin some- 

 times as large as the entire bod}' of the fish, which buo}^ it to the 

 surface and keep it there in spite of its struggles to descend. The 

 pipe-fish {Sqj^iostoma fuscuin) usually shows vesicles about the snout. 

 In the scup {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 sufiicient to 

 cause death. Aside from some occasional blood}' 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, pi. i), 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 



a In 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 miist have occnrred in spite of cardiac 

 effort. 



