1910.] Comparative Toxicity of Theobromine and Caffeine. 573 



abolition taking place in 12-5 minutes, followed by a slight recovery on 

 reintroducing saline solution. 



Saline Coffee Extract. 

 Similarly a 1-per-cent. extract produced no effect ; on substituting a 5-per- 

 cent, extract, the effect was almost instantaneous, and the recovery, though 

 incomplete, followed immediately after running in saline solution. After an 

 interval of 19 minutes a 2-5-per-cent. extract was substituted, which caused 

 a contracture with abolition in 12-5 minutes, followed by recovery on running 

 in saline solution. 



There do not appear to be any very marked differences between the 

 saline tea and coffee extracts; though possibly the contracture is more 

 marked in the case of the latter, the recovery is less marked in the case 

 of the former. Such a result would be probable, if the toxic effect both 

 of tea and of coffee is mainly due to the caffeine (theine) present, the tannic 

 acid, also a constituent of both, producing only a secondary effect as regards 

 muscle proteins. 



But with the extract of the " caffeine-free coffee " (fig. 5) there was 



no such marked contracture on adding a 5-per-cent. extract, and abolition 

 took place in (nearly) nine minutes ; in the case of a 2-5 extract, abolition took 

 place in 21 minutes, followed by recovery on substituting saline solution. The 

 differences between the effects produced by ordinary and " caffeine-free " 

 coffee are most marked, though in the case of the 2"5-per-cent. extracts they 

 would doubtless have been less pronounced if the experiments had been both 

 equally performed with a fresh muscle. 



Fig. 5. — Saline Coffee "freed from caffeine." Upper line 5 per cent. Lower line 2'5 per 



cent. 



