103 



saline cathartics in increasing th« contractions of the colon, 

 with evacuation of its contents, while the upper intestine 

 ren:ains unaffected or is actually inhibited (6, 7). 



Efffctii of Drur/s irhich parah/se or stimulate Nervous Tissues. 



Curari paralyses the nerve-endings of striated skeletal 

 muscles in the vertebrates, but it leaves the nerve-endings in 

 the heart unaffected. The muscles of different species are, 

 however, differently affected by curari, and certain species — 

 for example, fishes and the tortoise — are almost immune to its 

 effects (10). The muscles of worms are totally unaffected by 

 curari (11). In these experiments it was found that curari, 

 even in such high dosage as 1:1000 solution, either in m/8 

 NaCl or in a mixture of 50 mols. m/8 NaCl to 1 mol. m/8 

 CaClj, leaves the movements, both of the intestine and of the 

 rectum, totally unaffected. 



Atropine, on the contrary, while leaving the nerve- 

 terminations in the striated muscles of the vertebrates 

 unaffected, nevertheless paralyses the nerve-terminals in a 

 variety of smooth-muscle organs. The movements of the 

 mammalian intestine are, however, unaffected by atropine (12), 

 and in these experiments atropine sulphate in 1 : 1000 solu- 

 tion was similarly found to be devoid of effect. (2^ 



Nicotine first stimulates and then paralyses the peripheral 

 ganglia of the autonomic nervous system of the vertebrates. 

 In these experiments it exerted only a long-delayed toxic 

 action. Solutions containing 1 : 1000 of the free base caused 

 a gradual and progressive diminution of the frequency and 

 amplitude of contractions, but the intestine (or rectum) was 

 not brought to a standstill even after half an hour of exposure 

 to this solution. Washing with fresh saline solution immedi- 

 ately restored the original vigour of the contractions. 



Codeine, on the contrary, which has little or no effect upon 

 striated muscles or their nerv^e supply in vertebrates, brings 

 about almost instant cessation of all movements in the fly's 

 intestine. This corresponds to the usual action of small dosages 

 upon the unstriated muscle of the mammalian intestine. Tlie 

 following protocol of a typical experiment illustrates this effect, 

 a double plus sign being used to denote exceptionally vigorous 



(2) A solution is stated to be devoid of effect when no change in 

 rhythm or frequency is observed ^fter fifteen minutes. During 

 longer periods spontaneous changes of rhythm or amplitude may 

 occur which do not allow us to differentiate between the effects of 

 drugs and spontaneous deterioration of the tissue due to prolonged 

 exposure to abnormal conditions. 



