TEMP. -MAJOR H. M. EVANS ON THE STING-RAY. 4oli 



15. The Poison-Organ of the Sting-Ray (IVi/r/on pastiiiaca)^ 

 Bv Tempy.-Major H. Muir Evans, M.D. (Lond.),, 

 r".A.M.C.(T.).* 



[Received March 3, 1916 : Read April 18, 1916.] 

 (Text-figures 1-7.) 



Part I. Historical Summary. 



The question of the presence of true poison-orgtsns in fish is: 

 one which has exercised th.e minds of observers for centuries. 

 From Aristotle down to the end of the nineteenth century the 

 presence or absence of a poison-gland in the Sting-Ray has 

 remained an unrevealed secret, although many observers have 

 felt convinced that something besides the laceration by its 

 serrated spines was necessary to cause the pain and inflammation 

 that resulted from injuries produced by it. Even Bottard, tO' 

 whom I am indebted for most of the early historical literature,, 

 denied the presence of a poison apparatus ; and the ' Cambridge 

 ISTatui'al History' merely states (p. 177) that "among Elasmo- 

 branchs the Eagle-Rays [Aetobatis) and Sting-Rays {Trijgon) have 

 barbed or serrated spines on the tail, which inflict wounds far 

 more severe than those caused by mere mechanical laceration ; 

 but, except the mucus secreted by the gland cells of the skin, 

 which may possess venomous properties, no special poison-forming 

 glands in connection with the spines are at present known." 



Dr. Antonio Porta contributed a paper on venomous fish to- 

 the ' Anatomischer Anzeiger' of March 1, 1905. "It can be 

 seen, " he says (p. 235), " by what I have quoted above, that until 

 now it was not known that a poison apparatus existed in the 

 TrygonidaB and Myliobatidfe. The barb of the Trygon is almost 

 similar to that of the Myliobatides, but it is longer and narrower. 

 The said sting shows the lateral mai'gins deceitfully serrated 

 with the points turned from the back to the front. According 

 to Moreau, in a fish of a medium size, the dart is very nearly 

 one quarter of the length of the back, but there is nothing exact 

 in its proportion. In nine specimens ( T. violacea and T. pasti- 

 naoa) of medium size that I examined, I found that the length 

 of the dart vai'ied from 8-7 to 12"6 cm. It is renewed every 

 year of the life of the fish, and since sometimes the new one 

 sprouts before the old one falls off, we find individual fish armed 

 with two or, more rarely, three or four stings. If we isolate a 

 sting and examine it, we observe on the ventral aspect two 

 grooves on either side of a ridge which become shallow in width 

 and depth towards the base. In these two grooves the poison- 

 organs are situated, which penetrate to the deepest part of the 

 groove and there continue laterally and above into two small 



* Communicated by the Seceetary. 



