VARIETIES OF ACTION— DOSE. 231 



tating the nerve-centres, produces convulsions, which cease when 

 the action of the poison extends to other nerves. In this case 

 neither the muscles, the blood, nor the nerve-centres, are acted 

 on directly by the curare. The muscles will contract if stimu- 

 lated, and, if the lungs be artificially supplied with air, the blood 

 will be arterial ised as usual, the convulsions will cease, and life 

 may be preserved. These asphyxial convulsions, which are pro- 

 duced by the circulation of venous blood in the nerve-centres, 

 are thus due to the indirect action of curare. 



Local and Remote Action. — Before curare could reach the 

 nerves on which it acted directly, it was necessary for it to enter 

 the circulation, but it had no marked action on the spot wdience 

 it was absorbed. Other substances, however, produce an effect 

 on the spot to which they are applied, and this may be inde- 

 pendent of any effect which they produce after absorption. This 

 is termed their local action. Thus strong sulphuric acid taken 

 into the stomach combines with its tissues and forms a slough : 

 this is its local action. But besides this, the irritation in the 

 stomach produces through the nervous system a weakening effect 

 on the heart, the circulation stops, and the person dies. It is 

 not the sulphuric acid which has found its way into the circula- 

 tion and acted on the heart that arrests its pulsations, but the 

 irritation in the stomach which has influenced it through its 

 nerves. This is the remote edect of the acid. 



Dose. — The effect produced by any remedy depends on several 

 conditions. The first of these is the amount existing in the Uoocl 

 at any given time, which we may call the actual dose, to distin- 

 guish it from the usual dose administered by the stomach or 

 otherwise, a part of which may not be absorbed, but remain 

 inert at the point of introduction. The action which a drug has 

 on the body is not dependent on its absolute amount, but on the 

 proportion it bears to the body on which it is to act, so that an 

 amount which is a small dose for one person is a very large one 

 for another.* Thus if a grain of some active substance be 

 injected at the same time into the veins of a full-grown man and 

 into those of a boy of only half his weight, it will be distributed 

 through twice as much blood in the man as in the boy, and 



* Buchlieim, Arzneimiitellehre, p. G5. 



