204 



tions become increased as the tears, saliva, urine and mucus of the 

 air-passages, which effect appears to be owing to the paralysis of the 

 vascular nerves and consequent dilatation of the vessels caused by 

 the poison. 



16. In mammalia urari causes death by paralysis of the respi- 

 ratory nerves and suppression of the respiration, which brings on 

 convulsions in these animals as a collateral effect. In frogs the 

 final extinction of the functions may also be partly ascribed to sup- 

 pressed action of the lungs and defective oxidation of the blood, 

 which at length renders the heart unfit to perform its office ; but it 

 must be observed that in this case the cause of death is not so plain, 

 inasmuch as in these animals the functions are in a great degree 

 independent of the pulmonary respiration. 



II. STRYCHNIA. 



Some experiments with strychnia (the acetate) gave the following 

 results : 



1 . Strychnia has not the least influence on the peripheral nerves 

 through the blood, which is best shown by cutting the nerves before 

 administering the poison. 



2. Strychnia paralyses the motor nerves of the voluntary muscles 

 by exciting them to too energetic action, a paralysis which may be 

 compared to that caused by powerful electric currents acting upon 

 the nerves. In frogs, when the tetanic spasms are over, the nerves 

 often show no trace of excitability ; in mammalia they generally retain 

 it in a slight degree, but never show the same energy of action as 

 when uninjured. 



3. Strychnia does not affect the sensory nerves. 



4. The heart is not affected by strychnia, not even during the 

 tetanic spasms, with the exception only that its pulsations are some- 

 times a little slower during the tetanic state. On the contrary, the 

 lymph-hearts of frogs contract themselves as soon as the tetanus 

 begins, and remain in this state as long as the spasms last. 



5. The tetanic fits can be brought on in two ways ; first, through 

 the sensory nerves, which, by irritating the grey substance of the 

 spinal cord, produce the tetanic contractions as reflex movements ; 

 and, secondly, through the brain, which is not affected at all by 

 strychnia and preserves its powers of volition and sensation. Accord- 



