EFFECT OF SNAKE VENOM UPON THE NERVOUS SYSTEM, ETC. 129 



endings is found to be much quicker than that of the muscles themselves. 

 In order to produce a fuller effect of the venom upon the musculo-endings 

 he advises the employment of a weak solution or about 0.0000333 g m - (° r 

 1/30 mg.), 0.00005 gm. being a minimal lethal dose, for injection into the 

 dorsal lymph-sac of frogs; too large an amount kills the animal directly 

 from general paralysis without much curare-like action on the nerve endings. 

 He confirms the theory that the phrenic nerves are affected much earlier 

 than other motor nerves. 



Ragotzi did not observe acceleration of respiratory frequency at any stage 

 of the poisoning. The inhibitory end-plates of the vagus in the heart were 

 unaffected. In some animals the venom caused a rapid, transient weaken- 

 ing of the heart, which, however, regained its original activity very soon. 

 In the frog, when the venom is given intravenously it arrests the heart in sys- 

 tole at once, and Ragotzi considers this to be due to the direct effect upon 

 the cardiac muscle. In the case of subcutaneous injection, the heart stops in 

 diastole, due, according to this author, to the paralysis of the cardiac ganglia. 



Ragotzi emphasized that the spinal cord is not directly affected by cobra 

 venom, and that insensibility of the muscles to the stimuli through the spinal 

 cord is in most cases due to the end-plate paralysis of the motor nerves; 

 or, if there is any paralysis in the cord, it is of a secondary nature, chiefly due 

 to the insufficient blood supply caused by the venom. He recalls the possi- 

 bility of a fatal haemorrhage or thrombosis occurring in the regions of the 

 nerve centers when the fresh venom is employed. 



Elliot, Sillar, and Carmichael 1 found the effects of the venom of Bungarus 

 cceruleus, the common krait, on the nervous system to consist of paralysis 

 of the respiratory center, curare-like action on the nerve-endings, especially 

 affecting early those of the phrenic nerves, and dilatation of the splanchnic 

 vessels. The vasomotor center is strongly affected. The contraction of arte- 

 rioles and capillaries is produced, but not in so marked a degree as in the 

 cobra poisoning. 



Wall, and later Lamb, 2 made many important contributions to our knowl- 

 edge of the behavior of the venom of Bungarus fasciatus (banded krait). 

 In acute cases of poisoning death invariably came through respiratory failure, 

 with very pronounced paralysis of the limbs. In intravenous injection death 

 took place much earlier than in the case of subcutaneous administration of 

 the venom. Lamb is inclined to attribute the cessation of respiration to 

 paralysis of the respiratory center, but no effort has been made to ascertain 

 the extent to which the nerve-endings of certain motor nerves — especially 

 the phrenics — are affected. The changes produced by this venom in the 

 nervous system are chiefly chromatolytic degeneration throughout the entire 

 cerebro-spinal system. I intend to return to this more in detail in a later 

 section. 



1 Elliot, Sillar, and Carmichael. On the action of the venom of Bungarus cosruleus (the common krait). 



Roy. Soc. Proc, 1904, LXXIV, 108. 



2 Lamb. Some observations on the poison of the banded krait {Bungarus fasciatus). Sci. Mem. by 



Officers of the Med. and Sanit. Depts. of the Govern, of India, 1904, new series, No. 7. 



