PHYSIOLOGY. 87 



much to the purpose, is this : persons who stammer, or suffer a 

 considerable interruption from convulsive motions arising in 

 speaking, can, nevertheless, sing quite easily without any inter- 

 ruption ; which appears to be owing to this that in singing, 

 they have their ear to determine both the measure and order, 

 and, therefore, they go on without any interruption ; but when 

 they exert the organs of speech by the power of their own will, 

 they do so without any such measure. It is commonly from 

 some accidental bashfulness or hurry, that they fall into stam- 

 mering ; and I am of opinion, that in a person who stammered, 

 and was, at the same time, a very excellent mimic, the case 

 would be the same in imitating the sound and voice of other peo- 

 ple, as if he was singing, but in his own exertions he has no 

 such means of governing himself. This explains that it is the 

 loss of measure that throws us into convulsive and spasmodic 

 motions. 2. Direct stimulants. Gaubius (744.) mentions, 

 first, the mechanical and chemical acrimonies applied to the brain, 

 either directly, or by the intervention of other parts. He next 

 proceeds to the 'potentiae dolorificae,' I would rather have said 

 * dolor magnus acutus.' When we are taking notice of pains 

 producing convulsion and spasm, we observe that the effect of 

 violent pain is different in so far as it produces sometimes con- 

 vulsion and epilepsy, and at other times syncope. The one I 

 would refer to the stimulant powers ; and certainly if there are 

 any direct stimulant powers, we may find them in pain ; but when 

 pain acts by producing syncope it seems to operate as a very 

 strongly sedative power. Here, however, I would not rashly 

 conclude that the effects are opposite to what they are in the 

 former case, for they may be the same, only different in degree ; 

 and it may be made a question whether pain, producing syn- 

 cope, is not an instance of violent excitement producing con- 

 siderable collapse ; and whether it is not like the opposite effects 

 of electricity in exciting action, or in producing death. Gau- 

 bius then mentions the ' immodica repletio,' which deserves 

 particular attention : I have endeavoured to shew that a certain 

 fulness of the vessels of the brain is necessary to its excitement, 

 and that a certain increase of that tension and fulness, therefore, 

 is indeed a strong stimulus, which will continue -the excite- 

 ment, and prevent the coming on of the state of collapse ; there 



