6'2 HULLKTIN OF THK BUREAI' (iK FISHERIKS. 



PuIIlt.s {S/iln n'lilrs iiuivnhihiH) upon tlie, iipproiicli of dc.iitli wun; found to inllulf 

 iind delliito their bodies and to fj-nusli tlieir teetii <iuitc uudilily. The otiiiT symptom^ 

 were iiuieh the same as those deseril)ed for the scup. 



These phenoinenii (in those Hshes which die si)eedii.v) undoul)tediy sui;gest (h-atli 

 from asphj'xiation, and indeed this explanation has l)eon otiered to account Un- the 

 fatal efl'ects of fresh water upon salt-water tishes and vice versa (see p. KU.). A 

 careful comparison of the preceding phenomena with those manifested by scup 

 wiiich were allowed to die from asphyxiation (the water supply to the tank beint; 

 stx)pped) undoubtedly showed points of resemblance. There were in both cases dis 

 turbances of respiration, frantic endeavors to escape, and convulsive movements 

 ending in death. In both cases, fishes were observed to eject water from the moutli 

 while at the surface. There were, however, some characteristic ditlVrences in tlir 

 symptoms, indicating difl'erences in the physiological effects. 



Bert (1871) states of the goldfish that when placed in saltwater its respiration 

 is at first accelerated and then retarded. No such rule was found to obtain in the 

 case of the scup when allowed to die in fresh water, and indeed no constant clnintii 

 of rare occurred until shortly l)efore rc^spiration cesised. 



KFKKCT OF si IIFACK ABRASIONS. 



Bert (1883) notes that the I'emovu! of tlir nuicus from a jjortion of the skin of an 

 eel (fresh-water specimen) renders it \ ulncrabic to the efiiMts of salt water, which 

 maj' otherwise work no harm. 



Garrey (190.5). like Bert, holds that the integrity of the skin is an important 

 factor in determining whether oi- not lertaiu changes of iiiimHuiu shall prove fatal. 

 Furthermore, he argues that at least one salt-water lisli (/'. li.tvrovlUns) will die in 

 its normal medium if the skin be injured extensively: 



A large, number of healtliy speciiiu'iia were selected iiiiii about one-half the body surface demnled 

 of scales by gentle scraping with the edge of a scalpel, or the skin was removed o\'er an area of mic 

 square centimeter on each side; then they were divided into three lots and placed respectively inle 

 fresh, sea water diluted with an equal volume of distilled water, and normal sea water. Of those kept 

 in fresh water in every experiment from eighty to ninety jier cent died within twenty-four hours, while 

 all died in less than thirty-six hours. In normal sea water the fish suffered a similar fate, although 

 death did not intervene so soon. But of those kept in .sea water of one-half its normal concentratien 

 only three per cent were dead at a time when all thos;^ in the other two media had died, and .seventy 

 per cent were kept alive for four weeks, when the wounds were all healed and the exjieriments 

 discontinued. In these experiments, therefore, no deleterious effects (il)tain wlien the internal 

 and external media are ajiproximately isotonic. 



In the ca.se of the hypei'tonic or hypotonic .solutions, however, Garrey believed 

 chat the damaged integtuneut rendered possible a fatal osmotic action. 



A priori it does not seem probable that every considerable surface abrasion 

 ^hoidd prove fatal either to a marine or a fresh-water fish in its normal medium. 

 Indeed, we have abundant proof that the more hardy species can survive seriou.-. 

 nuitilations. Experiments of my own, moreover, .suggested by those of Garrey, givi- 

 results entirely contl-adietory to his. 



In exiierinienl .">. live of the l'S s[)ecimens of F. ,niij((liK were deprived of their 

 scales throughout an area of about 1 square centimeter on the shoulder region. Of 

 the IS tish ((j4 per cent) w liicli ilied during the lirst I'l hours, none were found to be 

 the .scraped ones. 



