796 



SCIENCE 



[N. S. Vol. XLI. No. 1065 



cently published- the following excellent sum- 

 mary of all that is definitely known concerning 

 shark intoxication. 



In North Greenland, where the dog plays such 

 a large part as draught animal for the sledge, the 

 shark fishery has the additional importance of 

 providing food for the dogs. In the dried condi- 

 tion especially shark flesh is an excellent dog 

 food; it gives the animals strength to sustain pro- 

 longed exertions without being fatigued. In the 

 fresh condition, on the other hand, it is dangerous 

 for the dogs; when they eat a quantity of it they 

 become heavy and subject to giddiness (they are 

 said to be "shark-intoxicated"); on driving a 

 short distance with them they begin to hang their 

 ears, tumble from side to side and at last fall 

 down in cramp convulsions, after which they can 

 not be got to move from the spot; in a couple of 

 minutes the dog may recover, but when it runs 

 again the whole body quivers and the dog has no 

 power to drag; at the same time, especially when 

 the weather is warm, the animal has diarrhea, its 

 feces are "squirted out" as greenish water; 

 sometimes the animal dies of the sickness. At 

 places where shark food is plentiful, however, the 

 dogs accustom themselves to eating a large amoimt 

 of it without being sick; but if they are driven in 

 the warm sunshine they may be very bad from it. 

 From dried shark flesh the dogs never become 

 "shark-intoxicated," yet they can also become 

 sick from it, as dried shark meat tends to swell 

 out in the stomachs of the dogs; the Greenlanders 

 therefore advise to give the dogs only small ra- 

 tions of dried shark meat and first to cut the 

 meat into long and narrow strips, so that the dogs 

 do not gulp down the whole at once, but can reg- 

 ularly work through it with the teeth. 



To explain these phenomena it may be said 

 that the fresh shark flesh contains a compound that 

 acts like alcohol; when the flesh is boiled, the 

 poisonous stuff is removed and the dogs can then 

 eat more of it without suffering than when the 

 meat is fresh. The poisonous substance is prob- 

 ably present everywhere in the body of the shark, 

 also in the cartilage. Eink was of the opinion 

 that the danger of the shark's flesh was due to its 

 containing a large amount of saline fluids, which 

 were totally swallowed down when the flesh was 

 eaten in the frozen condition. To clear up the 

 matter I consulted the veterinary surgeon S. 



2 "The Selachians of Greenland" ("Saertryk 

 af Mindeskrift for Jepetus Steenstrup") pp. 12- 

 14, 1914. 



Hjortlund, who lived for a couple of years in 

 North Greenland and there made investigations 

 on the infectious sickness of the dogs; he has 

 kindly sent me the following information. 



"These cases of poisoning, which in Greenland 

 always occur after eating fresh, raw meat of the 

 Greenland shark (Sominosus microcephalus) , both 

 in men and dogs, is without doubt due to a spe- 

 cific poison (a toxin) which occurs in its body. 

 Nothing indicates the correctness of Rink's view, 

 that the poisonous nature of fresh shark meat was 

 due to the large quantity of saline fluids it con- 

 tained, whilst many things speak against this 

 view. 



"Meanwhile, however, the question has not yet 

 been scientifically investigated and all we know 

 about it is exclusively based on empirical obser- 

 vations. 



' ' The clinical symptoms, of which — as men- 

 tioned above — ^tiredness, dullness, uncertain gait, 

 sensory disturbances and a profuse diarrhea are 

 the most in evidence, depend in virulence on the 

 quantity of meat taken, but in dogs can also be 

 intensified in mild weather and with bodily exer- 

 tion. In men, where the poison causes a similar 

 complex of symptoms, the sense disturbances both 

 objectively and subjectively give the same impres- 

 sion as acute alcohol poisoning. The symptoms of 

 poisoning may last a shorter or longer time, from 

 a couple of hours to a couple of days. They may 

 be very weak, almost unnoticeable, when the ani- 

 mal has only taken a small quantity; on the other 

 hand dogs have several times been known to die 

 under violent symptoms, almost apoplectic in. 

 character, a short time after they had eaten large 

 quantities of shark meat. 



' ' Of importance in judging of the nature of the 

 poisonous stuff or stuffs is the fact that the ani- 

 mals can gradually be accustomed to taking larger 

 and larger quantities of it. Obviously antitoxins 

 can be produced in the body of the dog, which 

 counteract the activity of the poison; in other 

 words, the animal can to a certain degree become 

 immune, and this gradually occurs spontaneously at 

 places where the dogs have constantly the oppor- 

 tunity of eating fresh shark meat. 



"The poison, however, is soluble in water and 

 can thus be extracted from the meat by thorough 

 washing. How far, on the other hand, it is de- 

 stroyed by heating to temperatures below 100° is 

 more doubtful. In any ease the transformation 

 here must proceed slowly; for according to all 

 reports the meat must be cooked in two to three 

 different waters before one can be certain that it 



