NEUROTOXINS OF SNAKE VENOM 153 



Kelvington ^ studied the central nervous system of rabbits killed by sub- 

 cutaneously injecting varying doses of the venom of Notechis scutatus, the 

 Australian tiger snake. The animals died within from 20 minutes to 36 

 hours, according to the amounts of the venom given. Death resulted from 

 the paralysis of respiration. There were no signs of inflammation present. 

 Except in the animal which died in 20 minutes after the administration of 

 the poison, the nerve cells exhibited signs of degeneration, which were most 

 marked in those animals which lived the longest (and which received the 

 smaller doses). 



The changes consisted in a breaking up of the Nissl granules into a fine, 

 dust-like deposit, which was scattered through the cell. This breaking-up 

 takes place apparently in several stages, smaller masses being formed which 

 subsequently subdivide. The disintegration of chromatic material takes 

 place either throughout the cell or unequally. A dust-like deposit can be 

 traced in the dendrites. The most extreme changes are seen in cells which 

 appear as shadows containing a few fully staining particles. Swelling of the 

 cell-body is not a noticeable feature, and though the nucleus loses its dis- 

 tinctness in outhne, it still, as a rule, remains in the center of the cell. The 

 nucleolus is nearly always present. 



The position of maximum intensity of the lesions was in the cells about 

 the central canal of the cord, viz, those at the inner side of the bases of 

 the anterior and posterior horns, and especially the small cells in the gray 

 commissure. 



In conclusion Kelvington made the following points as to the changes 

 observed in nerve cells after poisoning with notechis venom: 



(i) Chromatolysis, the Nissl granules breaking up into dust. Ultimately 

 all stainable substance disappears. 



(2) The staining never becomes diffuse. 



(3) No swelling of the cell occurs. 



(4) The outline of the nucleus is lost, but it retains its central position as 

 a rule. In the very worst cells the nucleus disappears. The nucleolus is 

 usually distinct, though it sometimes appears loose in the ceU. 



(5) The changes are very unequal in different cells. 



(6) The cells around the central canal of the cord show the earliest and 

 most advanced degeneration. 



(7) With rapidly fatal doses no microscopic changes occur. Its degree 

 is dependent on the time the animal survives. 



(8) Inflammatory and vascular changes are absent. 



Since 1904 Lamb and Hunter ^ have been studying the histological lesions 

 of the nervous system caused by various venoms of Indian snakes. The 



1 Kelvington. A preliminary communication on the changes in nerve cells after poisoning with the 



venom of the AustraUan tiger snake {Hoplocephalus curtus). Jour, of Physiol., 1902, XXVIII, 426. 



2 The Lancet, 1904, I, 20. Op. cit., 1904, II, 518. Op. cit., 1904, II, 1146; Venom of Bungarus 



fasciatus (banded krait). Op. cit., 1905, II, 886. Op. cit., 1906, II, 1231. Action of venoms 

 of different species of poisonous snakes on the nervous system. Op. cit., 1907, II, 1017; 

 Venom of Enhydrina valakadien. 



