A large lethal dose kills by this action, but the minimum lethal dose by its combined action on the respiration and the heart.
They are based on the experimental toxic, as distinguished from lethal dose.
So valuable are certain of the properties of atropine that it is often desirable to give doses of one-twentieth or onetenth of a grain; but these will never be ventured upon by the practitioner who is ignorant of the great interval between the minimum toxic and the minimum lethal dose.
It is also to be noted that, as in the case of poisons of known constitution, each toxin has a minimum lethal dose which is proportionate to the weight of the animal and which can be ascertained with a fair degree of accuracy.
The unit of antitoxin in Ehrlich's new standard is the amount requisite to antagonize i oo times the minimum lethal dose of a particular toxin to a guinea-pig of 250 grm.