484 PROFESSOR C. R. MARSHALL ON THE 



during the spawning season seemed to be less sensitive than frogs tested at other 

 times. But in all probability the variations were largely due to differences in the 

 rate of absorption into the blood and in diffusion along the lymph-sacs. The latter 

 mode of dissemination seemed to play an important part in many experiments with 

 tetra-ethyl-ammonium chloride especially. 



A noteworthy point seen in all the comparative experiments, and brought out in 

 the tables, is the marked diminution in activity of di-methyl-di-ethyl-ammonium 

 chloride as compared with tri-methyl-ethyl-ammonium chloride. A similar marked 

 but more qualitative change occurs in passing from tetra-ethyl-ammonium chloride 

 to methyl-tri-ethyl-ammonium chloride. The most characteristic feature of tetra- 

 ethyl-ammonium chloride intoxication in frogs is fibrillary tremors and coarse, 

 irregular muscular movements. These are more rarely seen, and when present are 

 much less pronounced in intoxications with other members of the series. They have 

 been most common and most distinct with methyl-tri-ethyl-ammonium chloride, and 

 least frequent and most transient with tetra-methyl-ammonium chloride, the other 

 two members occupying an intermediate position. 



Effect on Tadpoles. — The effects obtained on tadpoles by placing them in known 

 concentrations of the substances were similar to those seen in frogs, paralysis being 

 the most obvious symptom ; with tetra-ethyl-ammonium chloride, fine fibrillary 

 tremors of the tail were often noticed. Large tadpoles are much less susceptible 

 to these substances than small tadpoles, even when body-weight is taken into 

 consideration, and consequently they are not so well adapted for comparative 

 experiments. Solutions of various concentrations were used, but it will suffice to 

 give the results obtained from the most concentrated, except in the case of tetra- 

 methyl-ammonium chloride and tri-methyl-ethyl-ammonium chloride, isotonic 

 solutions of which produced immediate paralysis. The time of onset of the paralysis, 

 as shown mainly by the cessation of spontaneous movements, seemed to be the most 

 delicate index of the relative activity of these compounds, and this is given for small 

 tadpoles of approximately uniform size with the concentrations named in the 

 following table : — 



Time of Onset of Paralysis in Tadpoles. 



Tetra-methyl-ammonium chloride . 

 Tri-methyl-ethyl ammonium chloride 

 Di-methyl-di-ethyl-ammonium chloride 

 Methyl-tri-ethyl-ammonium chloride 

 Tetra-ethyl-ammonium chloride 



017 per cent., 5 mins. 

 0-38 ,', 5 „ 



14 „ 9 „ 



1-6 ., 40 „ 



17 „ 60 „ 



The tadpoles in the bath of methyl-tri-ethyl-ammonium chloride moved more 

 vigorously than those in the tetra-ethyl-ammonium chloride at the end of thirty 

 minutes, but, as the table shows, they were paralysed earlier. 



