128 VENOMOUS SNAKES AND THE PHENOMENA OF THEIR VENOMS 



inclined to suggest the reflex nature of salivation through irritation of the 

 gastric branches of the vagus. Whatever the primary effects may be, the 

 final result was always a diminution in the secretory function. 



In investigating the cause of respiratory failure in cobra poisoning, Brunton 

 and Fayrer called attention to the remarkable fact that the end-plates of the 

 phrenic nerves become completely insensible to the strongest stimuli, while 

 the sciatics and vagus still retain a considerable amount of irritability. Thus, 

 the ultimate arrest of respiration is probably due, in part, to paralysis of the 

 medulla, and, in part, to paralysis of the motor-nerve endings in the respi- 

 ratory muscles. 



In regard to the effects of cobra venom upon the enervation of the circu- 

 latory system, Brunton and Fayrer consider this venom to have almost no 

 direct paralytic effects. It is well known that the cause of death in cobra 

 poisoning is usually respiratory failure, with the heart still beating vigorously. 

 But when a concentrated solution of venom is directly introduced into the 

 circulation of frogs the heart stops at once in systole. The same is true when 

 an excised heart of frog is immersed in a strong venom solution. The cessa- 

 tion of the cardiac activity is not of a paralytic, but of a tetanic nature. This 

 cessation of an isolated heart can not be due to the stimulation of the inhib- 

 itory center contained within it; for atropin, which paralyzes inhibitory 

 ganglia, does not restore the movements. It is probably not due to the par- 

 alysis of motor ganglia, as the heart does not stop in diastole, but in systole, 

 and resists distention by fluid within it. Brunton and Fayrer thought that 

 the most probable cause was the stimulating effects of the venom upon the 

 heart, resulting in the tetanic state of the latter. The inhibitory branches of 

 the vagus are sometimes paralyzed. 



In this place it may be mentioned that the capillary circulation is not 

 unaffected, but is greatly increased after the injection of the poison. Judging 

 from the high blood pressure after the heart ceases to beat, the arterioles and 

 capillaries must be much contracted. 



Wall reached the conclusion that the principal action of cobra venom on 

 the nervous system consists of an extinction of functions, extending from 

 below upwards, of various nerve centers constituting the cerebro-spinal 

 system, and especially acting on the respiratory center and on those other 

 ganglia allied to it in the medulla, which are in connection with the vagus, 

 the spinal accessory, and hypoglossal nerves; and that it is directly to this 

 destructive action that we have to attribute death in most cases of cobra 

 poisoning. He observed an acceleration of the respiration rate, which does 

 not occur when the vagus is cut before the injection of the venom. 



Ragotzi, 1 going over practically the same field covered by the work of Brunton 

 and Fayrer, found that, if sufficient time elapses from the time of the injection 

 to the manifestation of the action, cobra venom affects and paralyzes the 

 intramuscular endings of the motor nerves. The paralysis of the nerve- 



' Ragotzi. Ueber die Wirkung des Giites der Naja tripudians. Virchow*s Archiv, 1890, CXXII, 201 . 



